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<pb> <C>NEW <I>EXPERIMENTS Phy$ico-Mechanicall Touching the Air.</I></C> <pb> <C>NEW EXPERIMENTS <I>Phy$ico-Mechanicall,</I> Touching</C> <C>The SPRING of the AIR, and its EFFECTS, (Made, for the mo$t part, in a New <I>PNEuMATICAL ENGINE</I>)</C> <C>Written by way of LETTER</C> <C>To the Right Honorable <I>Charles</I> Lord Vicount of <I>Dungarvan,</I> Elde$t Son to the EARL of <I>CORKE.</I></C> <C>By the Honorable <I>Robert Boyle</I> E$q;</C> <FIG> <C><I>OXFORD:</I> Printed by <I>H: Hall,</I> Printer to the Univer$ity, for <I>The: Robin$on.</I> 1660.</C> <pb> <FIG> <C>To the Reader.</C> <p><I>ALthough the following Trea- ti$e being far more prolix then becomes a Letter, and then I at fir$t intended it; I am very unwilling to en- crea$e the already exce$sive bulk of the Book by a Preface, yet there are $ome par- ticulars that I think my $elf oblig'd to take notice of to the Reader, as things, that will either concern him to know, or me to have known.</I> <p><I>In the fir$t place then: If it be demand- ed why I publi$h to the World a Letter, which by its Stile and diver$e Pa$$ages, appears to have been written as well For, as To a particular Per$on; I have chiefly the$e two things to an$wer: The one, That the Ex- periments therein related, having been ma- ny of them try'd in the pre$ence of Ingeni- ous Men; and by that means having made</I> <pb> <I>$ome noi$e among the</I> Virtuo$i (<I>in$omuch that $ome of them have been $ent into Fo- reign Countries, where they have had the luck not to be de$pi$'d) I could not without quite tyring more then one</I> Amanuen$is, <I>give out half as many Copies of them as were $o earne$tly de$ired, that I could not civilly refu$e them. The other, That intelligent Per$ons in matters of this kinde per$waded me, that the publication of what I had ob- $erv'd touching the Nature of the Air, would not be u$ele$s to the World; and that in an Age $o taken with Novelties as is ours, the$e n<*>w Experiments would be grateful to the Lovers of free and real Learning: So that I might at once comply with my grand De$ign of promoting Experimental and U$eful Philo$ophy, and obtain the great $a- tisfaction of giving $ome to ingenious Men; the hope of which, is, I confe$s, a tempta- tion that I cannot ca$ily re$i$t.</I> <p><I>Of my being $omewhat prolix in many of my Experiments, I have the$e Rea$ons to render, That $ome of them being altoge- ther new, $eem'd to need the being circum- $tantially related, to keep the Reader from di$tru$ting them: That divers Circum- $tances I did here and there $et down for fear of forgetting them, when I may hereafter</I> <pb> <I>have occa$ion to make u$e of them in my o- ther Writings: That in divers ca$es I thought it nece$$ary to deliver things cir- cum$tantially, that the Per$on I addre$$ed them to, might without mi$take, and with as little trouble as is po$sible, be able to re- peat $uch unu$ual Experiments: and that after I con$ented to let my Ob$ervations be made publick, the mo$t ordinary Rea$on of my prolixity was, That fore$eeing that $uch a trouble as I met with in making tho$e try- als carefully, and the great expence of time that they nece$$arily require, (not to mention the charges of making the Engine, and im- ploying a man to manage it) will probably keep mo$t men from trying again the$e Ex- periments; I thought I might doe the gene- rality of my Readers no unacceptable pe<*>ce of $ervice, by $o punctually relating what I carefully ob$erv'd, that they may look up- on the$e Narratives as $tanding Records in our new Pneumaticks, and need not reite- rate them$elves an Experiment to have as di$tinct an Idea of it, as may $uffice them to ground their Reflections and Speculations upon.</I> <p><I>And becau$e $ometimes 'tis the Di$cour$e made upon the Experiment that makes it appear prolix, I have commonly left a con-</I> <pb> <I>$picuous interval betwixt $uch Di$cour$es, and the Experiments whereunto they belong, or are annexed; that they who de$ire onely the Hi$torical part of the account we give of our Engine, may read the Narra- tives, without being put to the trouble of reading the Reflections too: Which I here take notice of, for the $ake of tho$e that are well ver$'d in the New Philo$ophy, and in the Mathematicks; that $uch may skip what was de$ign'd, but for $uch Per$ons as may be le$s acquainted even then I, with matters of this nature ($carce $o much as mention'd by any Writer in our Language) and not for them from whom I $hall be much more forward to learn, then to pretend to teach them. Of my being wont to $peak rather doubtfully, or he$itant- ly, then re$olvedly, concerning matters wherein I apprehend $ome difficulty, I have in another Treati$e (which may, through Gods A$si$tance, come abroad ere long) given a particular, and I hope a $atisfacto- ry account: Wherefore I $hall now defend my Practice but by the Ob$ervation of</I> Ari- $totle, <I>who $omewhere notes, That to $eem to know all things certainly, and to $peak po$itively of them, is a trick of bold and yong Fellows: Whereas tho$e that are in-</I> <pb> <I>deed intelligent and con$iderate, are wont to imploy more wary and diffident Expre$si- ons, or (as he $peaks)</I> <G><*>sife/ad<*> a)ei\ to\ <*>s, <*> to\ ta\xa</G>. <p><I>There are divers Reflections, and other Pa$$ages in the following Epi$tle, and even $ome Experiments (occa$ionally mention'd) which may $eem either impertinent or $u- perfluous, but are not $o: Being purpo$ely written, either to evince $ome truth oppo$'d, or di$prove $ome erroneous conceit main- tain'd, by $ome eminent New Philo$opher, or by $ome other Ingenious Men, who, I pre$um'd, would ea$ily forgive me the ha- ving on $uch occa$ions purpo$ely omitted their Names; though an inqui$itive Per$on will probably di$cover divers of them, by the mention of the Opinions di$prov'd in the Experiments I am excu$ing.</I> <p><I>Ever $ince I di$cern'd the u$efulne$s of $peculative Geometry to Natural Phi- lo$ophy, the unhappy Di$tempers of my Eyes, have $o far kept me from being much con- ver$ant in it, that I fear I $hall need the par- do<*> of my Mathematical Readers, for $ome Pa$$ages, which if I had been deeply skill'd in Geometry, I $hould have treated more ac- curately.</I> <pb> <p><I>And indeed, having, for Rea$ons el$e- where deduc'd, purpo$ely kept my $elf a $tranger to mo$t of the new</I> Hypothe$es <I>in Philo$ophy, I am $en$ible enough that the Engine I treat of has prevail'd with me to write of $ome $ubjects which are $ufficient- ly remote from tho$e I have been mo$t con- ver$ant in. And having been reduc'd to write the greate$t part of the en$uing Letter at a di$tance, not onely from my Library, but from my own Manu$cripts, I cannot but fear that my Di$cour$es do not onely want many choice things wherewith the Learned Writings of others might have en- riched or imbelli$hed them: But that partly for this Rea$on, and partly for that touch'd upon a little before, It is po$sible I may have mention'd $ome Notions already pub- li$h'd by others, without taking notice of the Authors, not out of any de$ign to defraud de$erving Men, but for want of knowing $uch particulars to have been already pub- li$h'd by them: E$pecially the Experiments of our Engine being them$elves $ufficient to hint $uch Notions as we build upon them.</I> <p><I>The order of the Experiments every Reader may alter, as $uits be$t with his own De$ign in peru$ing them; For not onely all</I> <pb> <I>tho$e betwixt whom there is an Affinity in Nature (by belonging to one $ubject) are not always plac'd one by another, but they are not $till $et down $o much as in the order wherein they were made; but mo$t common- ly in that ca$ual one wherein my occa$ions in- duc'd me to di$patch them to the Pre$s. And, which is wor$e, I did u$ually $end quite a- way the former Experiments, before the later were written, or perhaps $o much as made: Whereby I lo$t the advantage of cor- recting and $upplying the Imperfections of what I had formerly written, by the light of my $ub$equent Tryals and Di$coveries.</I> <p><I>Be$ides all this, the di$temper in my eyes forbidding me not onely to write my $elf $o much as one Experiment, but even to read over my $elf what I dictated to others. I can- not but fear, that be$ides the Authors mi$takes, this Edition may be blemi$h'd by many, that may be properly imputed to a very unskil- ful Writer (whom I was often times by ha$te reduc'd again$t my cu$tom to imploy) and may have e$caped the Diligence of that Learned Friend, that does me the favor to over-$ee the Pre$s; e$pecially there being the di$tance of two days Fourney betwixt it and me.</I> <p><I>I need not perhaps repre$ent to the equi-</I> <pb> <I>table Reader, how much the $trange Confu- $ions of this unhappy Nation, in the mid$t of which I have made and written the$e Experiments, are apt to di$turb that calm- ne$s of Minde, and undi$tractednc$s of Thoughts, that are wont to be requi$ite to Happy Speculations. But I pre$ume, that by all the$e things put together, he will readily perceive, That I have been $o far from following the Poets prudent Coun$el touching the $low Publication of Books de$ign'd to purcha$e credit by,</I> <p>—— Nonumque prematur in Annum <p><I>that I $uffer this Treati$e to come abroad into the World with a multitude of Di$ad- vantages.</I> <p><I>But if it be demanded, why then I did not make it f<*>ter for the Pre$s before I $ent it thither? my An$wer mu$t be, That not at fir$t imagining that this $ort of Experi- ments would prove any thing near $o trouble- $ome, either to make, or to Record, as I afterwards found them, I did, to engage the Printer to di$patch, promi$e him to $end him the whole Epi$tle in a very $hort time: So that although now and then the occa$ional vacations of the Pre$s, by rea$on of Fe$ti-</I> <pb> <I>vals, or the ab$ence of the Corrector, gave me the lei$ure to ex$paciate upon $ome $ub- ject; yet being oftentimes call'd upon to di$- patch the Papers to the Pre$s, my promi$e, and many unexpected Avocations, obliged me to a ha$te, which, though it have detract- ed nothing from the Faithfulne$s of the Hi$torical part of our Book, has (I fear) been di$advantageous enough to all the re$t. And I made the le$s $cruple to let the fol- lowing Papers pa$s out of my hands, with all their Imperfections; becau$e, as the publick Affairs, and my own, were then circum$tanc'd, I knew not when (if at all) I $hould be again in a condition to pro$ecute Experiments of this kinde; e$pecially, $ince (to omit my being almo$t weary of be- ing, as it were, confin'd to one $ort of Ex- periments) I am pre-ingag'd (if it plea$e God to vouch$afe me Life and Health) to imploy my fir$t lei$ure in the publication of $ome other Phy$iological Papers, which I thought 'twould make me much the $itter to take in hand, if I fir$t di$patch'd all that I had at this time to write touching our Engine.</I> <p><I>I have this further to adde, by way of Excu$e, That as it has been my de$ign in publi$hing the$e Experiments to gratifie</I> <pb> <I>Ingenious men; $o, if I have not been much flattered, I may hope that the vari- ous hints to be met with in the following Letter, will (at lea$t) $omewhat awaken mens thoughts, & excite them to new $pecula- tions ($uch as perhaps even inqui$itive men would $carce el$e light upon) and I need not de$pair, that even the examination of $uch new Su$picions and Enquiries will hence al- $o, at lea$t Occa$ionally be facilitated: I $aid Occa$ionally, becau$e it being, as 'tis proverbially $aid,</I> Facile Inventis addere. <I>It $eems not irrational to expect, that our Engine it $elf, and divers of our Experi- ments, will be much promoted by the Indu- $try of Inventive and Mathematical Wits, who$e contrivances may ea$ily either correct or $upply, and con$equently $urpa$s many of tho$e we have made u$e of. And, particu- larly, if Men by skill and patience can ar- rive both to evacuate $uch Receivers as ours, till there be no more Air left in them, then there $eems to have remain'd in the Gla$$es made u$e of about the Magdebur- gick Experiment (hereafter to be mention- ed) and to keep out the Air for a competent while, the U$efulne$s and Di$coveries of our Engine, will not be a little advanc'd. And perhaps that may belong to it, which I re-</I> <pb> <I>member</I> Seneca <I>$peaks of Nature,</I> Initia- tos (<I>$ays be</I>) nos credimus, in Ve$tibulo ejus hæremus: <I>For being now in a place where we are not quite de$titute of moderate- ly skilful Artificers, we have, $ince the Conclu$ion of the following Letter, made $ome Additions to our Engine, by who$e help we finde (upon $ome new tryals) that we may be able, without much of new trouble, to keep the ambient Air out of the exhau- $ted Receiver for a whole day; and perhaps we $hould be able to keep it out much longer, if before we $hall have di$patch'd $ome ur- gent Affairs, and publi$h'd $ome Papers for which a kinde of Promi$e is thought to make us Debtors to the Pre$s, we could be at lei- $ure to pro$ecute $uch Experiments, as may po$sibly afford a Supplement to the follow- ing Treati$e, from which I $hall now no lon- ger detain the Reader.</I> <p><I>I know</I> <pb> <FIG> <p>Friendly Reader, <p><I>I Know all Per$ons that have a publick Spirit for the Ad- vancement of Lear- ning, will think much that this piece came not out in a Lan- guage of more general U$e, then this you $ee it now attir'd in; e$pecially $ince the Excel- lent Noble Per$on, who is the Author, is known to be well a- ble him$elf (being almo$t uni- ver$ally a Lingui$t) to have gi- ven it either the Old Latin, or</I> <pb> <I>the newer French Dre$s.</I> <p><I>But if it be an Honor to a Language to be preferr'd, and this Honor breeds $ometimes an Emulation, as anciently it did between the</I> Greeks <I>and</I> Ro- mans, <I>it cannot be thought unhand$ome for an Engli$h Nobleman to have preferr'd his own: And it may be a $uf- ficient Rea$on for the Gentry of Forein Parts to learn our Speech, or keep Interpreters, that they are $ure to have for their requital, from many of our Engli$h Writers (as here from this piece) much curiou$ly ingenious, and profitable Lear- ning.</I> <pb> <p><I>But as to this particular (give me leave to u$e Words from a Story)</I> Since the Mountain cannot come to <I>Mahomet, Mahomet</I> will go to the Mountain<I>: I mean thus; Becau$e many witty Men, Per- $ons of Honor and E$tate e$pe- cially, may be $uppo$'d to be a- ble to make a better account, by employing their Studies and Time on Matter then Words, and $o are ju$tly impeded from learning Languages; And be- cau$e (as I may judge) the no- ble Author is willing to oblige all Men, He has already provi- ded, that this piece $hall $hort- ly be done into Latine, that $o</I> <pb> <I>it may come home to divers wor- thy Per$ons in its Stream, who cannot travel to finde it out in its fir$t Origine.</I> <p><I>Having therefore leave $o to do, I cannot forbear to give the World the Adverti$ement of this Latine Edition, le$t $ome skilful Arti$t $hould take needle$s pains about a Work, which will, ere long (by Gods furtherance) be done to his Hands; For $uch unprofitable expences of Study have too fre- quently happened, and too much to the di$advantage of Learn- ing, for want of a $ufficient Corre$pondence and Intercour$e between $uch as are exerci$ed</I> <pb> <I>in the Mines of Wi$dome.</I> <p><I>This is all the trouble I $hall at pre$ent give you: Nor $hall I need minde thee, if you have a true gu$t for the Book you read, to have an honor and thankful regard to the Per$on that has favor'd us with the Communi- cation of the$e his Tryals, & is manife$tly $o great a Patron and Friend to Experimental Learning, and all true Wi$dom; for $hould you fail in this, you might de$ervedly be depriv'd of $ome other Ob$ervations on the $ame $ubject, which the Au- thor, I heare, has made $ince the fini$hing of this Treati$e.</I> <p><I>I de$ire to be excu$ed that I</I> <pb> <I>not make Excu$es for the $low- ne$s of the Publication, hoping that the long expectation you have had of it, will enhance, and not dimini$h your delight in the enjoyment of a piece like to be, among$t the $tudents in accurate Philo$ophy, of $o generall accep- tance. Farewel.</I> <p>R: Sh. <FIG> <pb> <FIG> <C>A Summary of the chief Matters treated of in this Epi$tolical Di$cour$e.</C> <p><I>THe</I> Proæmium, <I>wherein is $et down the occa$ion of this Di$cour$e,</I> 1. <I>The mo- tives that induc'd the Author thereunto,</I> 2 &c. <I>The hints he received,</I> 5. <I>The things where- in this Engine excels any that have yet been made u$e of,</I> 6 &c. <I>The de$cription of the Engine and its parts,</I> 8 &c. <I>The way of pre- paring and u$ing it,</I> 15 &c. <I>The divi$ion of the Experiments tryable thereby into two $orts, and the difficulty of excluding the Air.</I> 18 &c. <p><I>The fir$t Experiment, touching the man- ner of pumping out the Air, and by what de- grees the Receiver is emptyed,</I> 20, &c. <I>A di- gre$sion touching the Spring or Ela$tical power of the Air, with an attempt for a Me- chanical Explication thereof, nece$$ary to be premi$'d for the explanation of the</I> Phæno- mena, <I>exhibited in this and the $ub$equent Experiments.</I> 22 &c. <p><I>The $econd Experiment, touching the pre$- $ure of the Air again$t the $ides of the Bodies it invirons,</I> 37 &c. <I>with a digre$sive Ex- plication of the pre$$ure of the Air included within an ambient Body.</I> 39 &c. <pb> <p><I>The third Experiment, touching the force requi$ite to draw down the Sucker,</I> 42 &c. <I>The Opinion of an eminent Modern Naturali$t examin'd.</I> 44 &c. <p><I>The fourth Experiment, touching the $welling of a Bladder; with the degrees by which it increa$es,</I> 45 &c. <I>Another Opini- on of a Learned Author examin'd.</I> 48 &c. <p><I>The fifth Experiment, touching the break- ing of a Bladder in the Receiver,</I> 49 &c. <I>And of another by heat.</I> 52 <p><I>The $ixth Experiment, of divers ways by which the ela$tical expan$ion of the Air was mea$ur'd.</I> 52 &c <p><I>The $eventh Experiment, touching what Figure does be$t re$i$t the pre$$ure of the Air.</I> 62 &c. <p><I>The eighth Experiment, tending to a fur- ther Demon$tration of the former, from the breaking of gla$s a Helmet inward.</I> 64 &c. <p><I>The ninth Experiment, contains a fur- ther confirmation from the breaking of a Gla$s outward,</I> 66 &c. <I>with an Experiment to prove, that the$e</I> Phænomena <I>proceed not from an invincible</I> Fuga vacui 69. <I>A de- $cription of other $mall Receivers, and their Conveniencies,</I> 70 &c. <I>A Receipt for the making of a Compo$ition to Cement crackt Gla$$es.</I> 73 <pb> <p><I>The tenth Experiment, touching the fla- ming of Candles inclo$ed in the Receiver.</I> 74 &c. <p><I>The eleventh Expertment, touching the burning of Coals,</I> 78. <I>And the la$ting of the excande$cence of an included piece of I- ron.</I> 80. <p><I>The twelfth Experiment concerning the burning of Match.</I> 82 <p><I>The thirteenth Experiment, concerning the further pro$ecution of the preceding, tending to prove the extinction of the Fire in the former Experiments, not to have proceeded from the pre$$ure of the Fire by the Fumes,</I> 84. <I>Some remarkable Circum$tan- ces of it,</I> 86. <I>The Experiment of Match try'd in a $mall Receiver.</I> 87 <p><I>The fourteenth Experiment, touching the $triking Fire, and kindling of Powder with the Lock of a Pi$tol in the evacuated Recei- ver.</I> 88 &c. <p><I>The fifteenth Experiment, touching the un$ucce$sfulne$s of kindling included Bo- dies with a burning Gla$s, and the Au- thors intention to pro$ecute it further.</I> 102 <p><I>The $ixteenth Experiment, concerning the operation of the Load$tone.</I> 105, &c. <pb> <p><I>The $eventeenth Experiment, touching the gradual de$cent of the Quick-$ilver in the Torricellian Experiment,</I> 106 &c. <I>Some ob$ervable Circum$tances concerning it,</I> 112 &c. <I>The $ame Experiment try'd in one of the $mall Receivers,</I> 115. <I>How this Experiment may be made u$e of to know the $trength of the pre$$ure of the Air for every degree of Rarefaction,</I> 116 &c. <I>The tryal of the $ame Experiment in a Tube not two foot long,</I> 118. <I>The rai$ing of the Mer- curial Cylinder, by the forcing of more Air into the Receiver,</I> 119. <I>Some Allegations for and again$t a</I> Vacuum <I>con$ider'd,</I> 120 &c. <I>Some Adverti$ements concerning the inconveniencies that may ari$e from the di- ver$ity of mea$ures made u$e of for the defi- ning the Altitute of the Mercurial Cylinder; and from the neglect of little parcels of Air apt to remain between the Mercury and the concave $urface of the Tube,</I> 123 &c. <I>Some Expedients for the more exact filling the Tube,</I> 127. <I>The height the Author once found of the Mercurial Cylinder, according to En- gli$h mea$ure.</I> 128. <p><I>The eighteenth Experiment, containing a new Ob$ervation touching the variation of the height of the Mercurial Cylinder in the $ame Tube, with an o$$er at the rea$on</I> <pb> <I>thereof.</I> 129 &c. <p><I>The</I> 19<SUP>th</SUP> <I>Experiment, touching the $ub- $iding of a Cylinder of Water,</I> 140 &c. <I>The $ame try'd in a $mall Receiver.</I> 143 <p><I>The</I> 20<SUP>th</SUP> <I>Experiment, touching the</I> Ela- ter <I>of Water, with a digre$sive Experiment to the $ame purpo$e</I> 144 &c. <p><I>The</I> 21 <I>Experiment, being a pro$ecution of the former Enquiry, by Experimenting the Generation of Bubbles under Water, a recital of $ome notable Circum$tances, with $ome ob$ervable Corollary's deduc'd there- from.</I> 147 &c. <p><I>The</I> 22<SUP>d</SUP> <I>Experiment, tending to a deter- mination of the Enquiry propo$'d in the for- mer Experiment, by proving the matter of the$e Bubbles from their permanency to be Air: The Experiments try'd in the great and $mall Receivers, evincing the $ame thing,</I> 155 &c. <I>An Experiment wherein there appear'd Bubbles in Quick-$ilver,</I> 160. <I>The Authors Inference,</I> 162. <I>A di- gre$sive Enquiry, whether or no Air may be generated anew; with $everal Hi$tories and Experiments, tending to the re$olving and clearing thereof.</I> 162 &c <I>The Authors ex- cu$e for $o long a Digre$sion.</I> 181 <p><I>The</I> 23<SUP>d</SUP> <I>Experiment, containing a fur- ther Enquiry touching Bubbles mad with</I> <pb> <I>common and di$till'd Water.</I> 182 <p><I>The</I> 24<SUP>th</SUP> <I>Experiment, wherein the inqui- ry is pro$ecuted with other Liquors, as with Sallet Oyl, Oyl of Turpentine, a Solution of Tartar, Spirit of Vinegar, Red-wine, Milk, Hen's Eggs, Spirit of Urine, Spirit of Wine and Water, Spirit of Wine.</I> 187 &c. <I>The wonderful expan$ion of the Spirit of Wine.</I> 194 <p><I>The</I> 25<SUP>th</SUP> <I>Experiment, touching the ex- pan$ion and gravity of the Air under wa- ter.</I> 195 &c. <p><I>The</I> 26<SUP>th</SUP> <I>Experiment, touching the Vi- brations of a</I> Pendulum. 202 &c. <p><I>The</I> 27<SUP>th</SUP> <I>Experiment, touching the pro- pagation of $ound: And the Authors inten- tion of trying $ome other Experiments, for the further elucidation thereof.</I> 210 &c. <p><I>The</I> 28 <I>Experiment, touching the $udden cruption of Bubbles from the water, when the airs pre$$ure was $peedily remov'd.</I> 214 <p><I>The</I> 29 <I>Experiment, touching the cau$e of the a$cent of Fumes and Vapors, wherein 'tis prov'd (from the $everal motions, which the Fumes of a $trange $moaking Liquor, of the Authors, were ob$erv'd to have in the Re- ceiver, upon the ex$uction of the Air) that the rea$on of their a$cent proceeds from the gravity of the ambient air, and not from any po$itive levity of their own.</I> 217 &c. <pb> <p><I>The</I> 30 <I>Experiment, concerning the na- ture of a fluid Body, illu$trated by the exam- ple of $moak which in $everal circum$tances $eems very much to re$emble the property of a fluid Body,</I> 224 &c. <I>A conjecture of the cau$e of the Suns undulation.</I> 228 <p><I>The</I> 31 <I>Experiment, concerning the</I> Phæ- nomena <I>of two flat Marbles exactly plain'd and wrought together, and the true rea$on thereof,</I> 229. <I>The Authors intention for the further pro$ecution thereof, & what hindred him; the rea$on why the under Marble did not fal from the upper (being onely conjoynd with Spirit of Wine) when the Receiver was evacuated. And a notable relation concern- ing the cohe$ion of flat Bodies.</I> 231 &c. <p><I>The</I> 32 <I>Experiment, touching the forcible pre$$ure of the Air again$t the outward $u- perficies of a Valve, fa$ten'd upon the $top- cock of the Receiver. The Diameter of it, and the weight it $u$tain'd.</I> 233 &c. <p><I>The</I> 33 <I>experiment, touching the great pre$- $ure of the Air again$t the under $uperficies of the Sucker,</I> 236 &c. <I>what weight was re- qui$ite to depre$s it, & what weight it would lift and carry up with it,</I> 239 &c. <I>what im- provement & u$e there may be made of this experiment,</I> 242. <I>A Di$cour$e touching the nature of Suction, proving that</I> fuga vacui <I>is not the adequate cau$e thereof.</I> 243 &c. <pb> <p><I>The</I> 34<SUP>th</SUP> <I>Experiment, containing $everal attempts for the weighing of light Bodies in the exhau$ted Receiver.</I> 258 &c. <p><I>The</I> 35<SUP>th</SUP> <I>Experiment, touching the cau$e of Filtration, and the ri$ing of Water in</I> Siphons, 262 &c. <I>A relation of a new kinde of</I> Siphon, <I>of the Authors, upon the occa$ion of trying the Experiment lately ob$erv'd by $ome French-men, and fur- ther improv'd by him$elf; and $ome conje- ctures touching the cau$e of the exhibited</I> Phænomena. 267 &c. <p><I>The</I> 36<SUP>th</SUP> <I>Experiment, touching the weigh- ing of a parcel of Air in the exhau$ted Ve$- $el; and $ome other Ob$ervations for the ex- plication thereof,</I> 272 &c. <I>An accidental Experiment, tending to the further confir- mation of the Authors Reflections upon the fir$t Experiment; with a digre$sive Ob$er- vation, noting the $ubtil penetrancy of $ome Spirits, to exceed by far that of the Air,</I> 275 &c. <I>And $ome other Experiments to $hew the difficulty of the ingre$s of the Air into the pores or holes of $ome bodies into which Wa- ter will readily in$inuate it $elf,</I> 279 &c. <I>with a conjecture at the cau$e thereof,</I> 282. <I>The Author returns to the pro$ecution if the in- quiry after the gravity of the Air: But fir$t, (upon the occa$ion of the tenacity of a thin</I> <pb> <I>Bubble of Gla$s) $ets down his thoughts con- cerning the $trange exuperancy of $trength in Air, agitated by heat, above what the $ame has unagitated,</I> 283 &c. <I>And then pro- ceeds to the examination of the weight of the Air by an</I> Æolipile, <I>and compares the re$ult thereof, with that of</I> Mer$ennus, 286. <I>The Opinions and Experiments of divers Au- thors, and $ome of his own, touching the proportion of weight betwixt Water and Air, are compar'd and examin'd by the Author,</I> 288. <I>The re$ult thereof,</I> 290. Mer$ennus <I>his ob$ervation reconcil'd, with that of the Author; and the proportion between the gra- vity of Water and Air about</I> London, 291 &c. <I>After the recital of the Opinions of $e- veral Writers, touching the proportion of gravity between Water and Quick-$ilver, the Author $ets down his own tryals, made $everal ways, together with his conclu$ion therefrom,</I> 293 &c. <I>The u$e he makes of this inquiry for the ghe$sing at the height of the Atmo$phere,</I> 297. <I>What other Experiments are requi$ite to the determination thereof.</I> 299 &c. <p><I>The</I> 37<SUP>th</SUP> E<I>xperiment, touching the $trange and odde</I> Phænomenon, <I>of the $udden fla$h- es of light in the cavity of the Receiver; the $everal circum$tances and difficulties of it,</I> <pb> <I>with $ome attempts towards the rendering at rea$on thereof,</I> 301, &c. <I>The Difficulty of $o doing fnr- ther $hewn from the con$ideration of the various changes of Air which doe not immediatly fall un- der our $en$es,</I> 315. <I>this la$t propo$ition prou'd by $everall ob$ervations.</I> 316. <p><I>The</I> 38. <I>Experiment, touching the freezing of water,</I> 319. &c. <I>Aproblem, (concerning the great force wherewith a freezing Liquor extends its $<*>lfe,) propo$'d upon the Con$ideration of divers admirable effects wrought thereby.</I> 320 &c. <p><I>The</I> 39. <I>Experiment, containing an inqui$ition after the temperature of the $ub$tance that remain'd in the cavity of the Receiver, after the Air was well exhau$ted. The relation of a</I> Phænomenon, <I>$eeming to proceed from the $welling of the Gla$s. With an adverti$ement concerning the pliablene$s of Gla$s in $mall peices.</I> 322. &c. <p><I>The</I> 40. <I>Experiment, touching the difficulty that occur'd in making tryall whether rarified Air were able to $u$taine flying in$ects.</I> 326. &c <p><I>The</I> 41. <I>Experiment, Exhibiting $everall try- alls touching the re$piration of divers $orts of ani- malls included in the Receiver,</I> 328, &c. <I>With a digre$$ion containing $ome doubts touching re$pira- tion wherein are delivered $everall Experiments re- lating thereunto.</I> 335 &c. <p><I>The</I> 42. <I>Experiment, touching the differing o- peration of corro$ive Liquors in the emptied Receiver and in the open Air.</I> 384 <p><I>The</I> 43. <I>Experiment, touching the $pontaneous E- bullition of warm Liquors in the exhau$ted Receiver.</I> 388 <p><I>The Conclu$ion.</I> 394 <pb> <FIG> <pb> <FIG> <pb> <FIG> <pb> <FIG> <pb n=1> <FIG> <C>TO THE LORD OF <I>DUNGARVAN,</I> My Honoured and Dear NEPHEW.</C> <p><I>My Dear Lord,</I> <p>REceiving in your la$t from <I>Paris,</I> a de$ire that I would adde $ome more Experi- ments to tho$e I formerly $ent You over: I could not be $o much your Servant as I am, without looking upon that De$ire as a Com- mand; and con$equently, without think- ing my $elf obliged to con$ider by what $ort of Experiments it might the mo$t ac- ceptably be obey'd. And at the $ame <pb n=2> time, perceiving by Letters from $ome other Ingenious Per$ons at <I>Paris,</I> that $e- veral of the <I>Virtuo$i</I> there, were very intent upon the examination of the Inte- re$t of the Ayr, in hindring the de$cent of the Quick-$ilver, in the famous Expe- riment touching a <I>Vacuum:</I> I thought I could not comply with your De$ires in a more fit and $ea$onable manner, then by pro$ecuting and endeavoring to promote that noble Experiment of <I>Torricell<*>s:</I> and by pre$enting your Lord$hip an ac- count of my attempts to illu$trate a $ub- ject, about which, it's being $o much di$- cour$'d of where you are, together with your inbred Curio$ity, and love of Ex- perimental Learning, made me $uppo$e you $ufficiently inqui$itive. <p>And though I pretend not to acquaint you, on this occa$ion, with any $tore of new Di$coveries yet po$$ibly I $hall be $o happy, as to a$$i$t you to <I>know</I> $omethings which you did formerly but <I>$uppo$e;</I> and $hall pre$ent you, if not with new Theo- ries, at lea$t with new <I>Proofs</I> of $uch as are not yet become unque$tionable. And if what I $hall deliver, have the good for- tune to encourage and a$$i$t you to pro$e- cute the Hints it will afford, I $hall ac- <pb n=3> count my $elf, in paying of a duty to you, to have done a piece of Service to the Commonwealth of Learning. Since it may highly conduce to the advance- ment of that Experimental Philo$ophy, the effectual pur$uit of which, requires as well a Pur$e as a <*>in, to endeere it to <I>hopeful</I> Per$ons of your Quality: who may accompli$h many things which o- thers can but <I>wi$h</I> or, at mo$t, but <I>de$ign,</I> by being able to imploy the Pre$ents of Fortune in the $earch of the My$teries of Nature. <p>And I am not faintly induc'd to make choice of this Subject, rather then any of the expected Chymical ones, to enter- tain your Lord$hip upon, by the$e two Con$iderations: The one, That the Ayr being $o nece$$ary to humane Life, that not onely the generality of Men, but mo$t other Creatures that breath, can- not live many <I>minutes</I> without it; any con$iderable di$covery of its Nature, $eems likely to prove of moment to Man-kinde. And the other is, That the Ambient Ayr, being that whereto both our own Bodies, and mo$t of the others we deal with here below, are almo$t per- petually contiguous; not onely its alte- <pb n=4> rations have a notable and manife$t $hare in tho$e obvious effects, that men have already been invited to a$cribe thereunto $uch as are the various di$tempers inci- dent to humane Bodies, e$pecially if cra- zy, in the Spring, the Autumn, and al$o on mo$t of the great and $udden changes of Weather) but likewi$e, that the fur- ther di$covery of the nature of the Ayr, will probably di$cover to us, that it con- curs more or le$s to the exhibiting of ma- ny <I>Phænomena,</I> in which it hath hither- to $carce been $u$pected to have any inte- re$t. So that a True Account of any Experiment that is New concerning a thing, wherewith we have $uch con$tant and nece$$ary intercour$e, may not one- ly prove of $ome advantage to humane Life, but gratifie Philo$ophers, by pro- moting their Speculations on a Subject which hath $o much opportunity to $olli- cite their Curio$ity. <p>And I $hould immediately proceed to the mention of my Experiments, but that I like too well that worthy $aying of the Naturali$t <I>Pliny, Benignum e$t</I> <MARG><I>In <*>. lib.</I> 1.</MARG> <I>& plenum ingenui pudor is, fateri per quos profeceris,</I> not to con- form to it, by acquainting your Lord- <pb n=5> $hip, in the fir$t place, with the Hint I had of the Engine I am to entertain you of. You may be plea$'d to remember, that a while before our $eparation in <I>Eng- land,</I> I told you of a Book that I had heard of, but not peru$'d, publi$h'd by the indu$trious Je$uit <I>Schottus,</I> wherein 'twas $aid, He related how that ingenious Gentleman <I>Otto Gericke,</I> Con$ul of <I>Mag- deburg,</I> had lately practiced in <I>Germany</I> a way of emptying Gla$s Ve$$els, by $uck- ing out the Ayr at the mouth of the Ve$- $el, plung'd under water: And you may al$o perhaps remember, that I expre$$'d my $elf much delighted with this Expe- riment, $ince thereby the great force of the external Air (either ru$hing in at the open'd Orifice of the empty'd Ve$$el, or violently forcing up the Water into it) was rendred more obvious and con$picu- ous, than in any Experiment that I had formerly $een. And though it may appear by $ome of tho$e Writings I $ometimes fhew'd your Lord$hip, that I had been $ol- licitous to try things upon the $ame ground; yet in regard this Gentleman was before-hand with me in producing $uch con$iderable effects, by means of the ex$uction of Air, I think my $elf oblig'd <pb n=6> to acknowledge the A$$i$tance, and En- couragement the Report of his perfor- mances hath afforded me. <p>But as few inventions happen to be at fir$t $o compleat, as not to be either ble- mi$hd with $ome deficiencies needful to be remedy'd, or otherwi$e capable of im- provement: $o when the Engine we have been $peaking of, comes to be more attentively con$ider'd, there will appear two very con$iderable things to be de- $ir'd in it. For fir$t, the <I>Wind-Pump</I> (as $ome body not improperly calls it) is $o contriv'd, that to evacuate the Ve$$el there is requir'd the continual labor of two $trong men for divers hours. And next (which is an imperfection of much greater moment) the Receiver, or Gla$s to be empty'd, con$i$ting of one entire and uninterrupted Globe and Neck of Gla$s; the whole Engine is $o made, that things cannot be convey'd into it, where- on to try Experiments: So that there $eems but little (if any thing) more to be expected from it, then tho$e very few <I>Phænomena</I> that have been already ob- $erv'd by the Author, and Recorded by <I>Schottus.</I> Wherefore to remedy the$e Inconveniences, I put both Mr. <I>G.</I> <pb n=7> and <I>R. Hook</I> (who hath al$o the Honor to be known to your Lord$hip, and was with me when I had the$e things under con$i- deration) to contrive $ome Air Pump, that might not, like the other, need to be kept under water (which on divers oc- ca$ions is inconvenient) & might be more ea$ily manag'd: And after an un$ucce$sful try all or two of ways propo$'d by o- thers, the la$t nam'd Per$on fitted me with a Pump, anon to be de$crib'd. And thus the fir$t Imperfection of the <I>German</I> Engine, was in good mea$ure, though not perfectly, remedy'd: And to $upply the $econd de$ect, it was con$idered that it would not perhaps prove impo$$ible to leave in the Gla$s to be empty'd, a hole large enough to put in a Mans Arm cloath'd; and con$equently other Bodies, not bigger then it, or longer then the in- $ide of the Ve$$el. And this De$ign $eem'd the more hopefull, becau$e I re- membred, that having $everal years be- fore often made the Experiment <I>De Va- cuo</I> with my own hands; I had, to exa- mine $ome conjectures that occurr'd to me about it, cau$ed Gla$$es to be made with a hole at that end, which u$es to be $eal'd up, and had neverthele$s been able <pb n=8> as occa$ion requir'd, to make u$e of $uch Tubes, as if no $uch holes had been left in them; by devi$ing $topples for them, made of the common Plai$ter call'd <I>Dia- chylon:</I> which I rightly enough ghe$$'d, would, by rea$on of the exqui$ite com- mixtion of its $mall parts, and clo$ene$s of its texture, deny all acce$s to the ex- ternal Air. Wherefore, $uppo$ing that by the help of $uch Plai$ters, carefully laid upon the commi$$ures of the $topple and hole to be made in the Receiver, the external Air might be hindred from in$i- nuating it $elf between them into the Ve$- $el, we cau$'d $everal $uch Gla$$es, as you will finde de$crib'd a little lower, to be blown at the Gla$s-hou$e; and though we could not get the Work-men to blow any of them $o large, or of $o conveni- ent a $hape as we would fain have had; yet finding one to be tolerably fit, and le$s unfit then any of the re$t, we were con- tent to make u$e of it in that En- gine: Of which, I $uppo$e, you by this time expect the De$cription, in order to the Recital of the <I>Phænomena</I> exhibited by it. <p>To give your Lord$hip then, in the fir$t place, $ome account of the Engine it <pb n=9> $elf: It con$i$ts of two principal parts; a gla$s Ve$$el, and a Pump to draw the Air out of it. <p>The former of the$e (which we, with the Gla$s men, $hall often call a Receiver, for its affinity to the large Ve$$els of that name, u$ed by Chymi$ts) con$i$ts of a Gla$s with a wide hole at the top, of a cover to that hole, and of a $top-cock fa$tned to the end of the neck, at the bottom. <p>The $hape of the Gla$s, you will find expre$$'d in the fir$t Figure of the annex- ed Scheme. And for the $ize of it, it contain'd about 30 Wine Quarts, each of them containing near two pound (of 16 Ounces to the pound) of water: We $hould have been better plea$'d with a more capacious Ve$$el, but the Gla$s-men profe$$ed them$elves unable to blow a larger, of $uch a thickne$s and $hape as was requi$ite to our purpo$e. <p>At the very top of the Ve$$el, (A) you may ob$erve a round hole, who$e Dia- meter (B C) is of about four inches; and whereof, the Orifice is incircled with a lip of Gla$s, almo$t an inch high: For the making of which lip, it was requi$ite (to mention that upon the by, in ca$e <pb n=10> your Lord$hip $hould have $uch another Engine made for you) to have a hollow and tapering Pipe of Gla$s drawn out, whereof the Orifice above mentioned was the Ba$is, and then to have the cone cut off with a hot Iron, within about an Inch of the Points (B C.) <p>The u$e of the lip, is to $u$tain the cover delineated in the $econd Figure; where (D E) points out a bra$s Ring, $o ca$t, as that it doth within and without cover the lip (B C) of the fir$t Figure, and is cemented on upon it with a $trong and clo$e Cement. To the inward taper- ing Orifice of this Ring (which is about three Inches over) are exqui$itely ground the $ides of the Bra$s $topple (F G;) $o that the concave $uperficies of the one, and the convex of the other, may touch one another in $o many places, as may leave as little acce$s, as po$$ible, to the ex- ternal Air: And in the mid$t of this cover is left a hole (H I) of about half an inch over, invironed al$o with a ring or $ocket of the $ame mettal, and fitted likewi$e with a bra$s $topple (K) made in the form of the Key of a $top-cock, and exactly ground into the hole (H I) it is to fill; $o as that though it be turn'd round in the <pb n=11> cavity it po$$e$$es, it will not let in the Air, and yet may be put in or taken out at plea$ure, for u$es to be hereafter men- tioned. In order to $ome of which, it is perforated with a little hole, (8) traver$ing the whole thickne$s of it at the lower end; through which, and a little bra$s Ring (L) fa$tned to one $ide, (no matter which) of the bottom of the $topple (FG) a $tring (8, 9, 10) might pa$s, to be imploy'd to move $ome things in the capacity of the empty'd Ve$$el; without any where un$topping it. <p>The la$t thing belonging to our Recei- ver, is the $top-cock de$igned in the fir$t Figure by (N.) for the better fa$tening of which to the neck, and exacter exclu$i- on of the Air, there was $oder'd on to the $hank of the Cock (X) a Plate of Tin, (MTUW) long enough to cover the neck of the Receiver. But becau$e the cementing of this was a matter of $ome difficulty, it will not be ami$s to mention here the manner of it, which was, That the cavity of the tin Plate was fill'd with a melted Cement, made of Pitch, Ro$in, and Wood-a$hes, well in- corporated; and to hinder this liquid Mixture from getting into the Orifice (Z) <pb n=12> of the $hank, (X) that hole was $topt with a Cork, to which was fa$tned a $tring, whereby it might be pull'd out of the up- per Orifice of the Receiver; and then, the gla$s neck of the Receiver being well warm'd, was thru$t into this Cement, and over the $hank whereby it was effected, that all the $pace betwixt the tin Plate and the Receiver, and betwixt the internal $uperficies of the Receiver, and the $hanck of the Cock, was filld with the Cement; and $o we have di$pach'd the fir$t and upper part of the Engine. <p>The undermo$t remaining part con$i$ts of a Frame, and of a $ucking Pump, or as we formerly call'd it, an Air Pump, $up- ported by it: The Frame is of Wood, $mall, but very $trong, con$i$ting of three legs, (111) $o plac'd, that one $ide of it may $tand perpendicular, that the free motion of the hand may not be hindered. In the mid$t of which frame, is tran$ver$ly nail'd a board, (222) which may not im- properly be call'd a Midriff, upon which re$ts, and to which is $trongly fa$tned, the main part of the Pump it $elf, which is the onely thing remaining to be de$cri- bed. <p>The Pump con$i$ts of four parts, a <pb n=13> hollow Cylindre, a Sucker, a handle to move that Sucker, and a Valve. <p>The Cylindre was (by a pattern) ca$t of bra$s; it is in length about 14 inches, thick enough to be very $trong, notwith- $tanding the Cylindrical cavity left with- in it; this cavity is about three inches Diameter, and makes as exact a Cylin- dre as the Artificer was able to bore. This hollow Cylindre is fitted with a $uck- er, (4455) con$i$ting of two parts, the one (44) $omewhat le$s in Diameter then the cavity of the Cylindre, upon which is nail'd a good thick piece of tan'd $hoe Leather, which will go $o clo$e to the Cylindre, that it will need to be very forcibly knock'd and ram'd in, if at any time it be taken out, which is therefore done, that it may the more exactly hin- der the Air from in$inuating it $elf be- twixt it and the $ides of the Cylindre whereon it is to move. <p>To the mid$t of this former part of the Sucker is $trongly fa$tned the other, namely a thick and narrow plate of Iron, (55) $omewhat longer then the Cylindre, one of who$e edges is $mooth, but at the other edge it is indented (as I may $o $peak) with a row of teeth delineated in <pb n=14> the Scheme, into who$e intervals are to be fitted, the teeth of a $mall Iron nut; (<*>) (as Trade$-men call it) which is fa$t- ned by two $taples (22) to the under $ide of the formerly mention'd tran$ver$e board (222) on which the Cylindre re$ts, and is turn'd to and fro by the third piece of this Pump, namely, the handle or <I>manubrium,</I> (7) of which the Figure gives a $ufficient de$cription. <p>The fourth and la$t part of this Cylin- dre, is the Valve, (R) con$i$ting of a hole bored through at the top of the Cy- lindre, a little tapering towards the cavi- ty; into which hole is ground a tapering Peg of bra$s, to be thru$t in, and taken out at plea$ure. <p>The Engine being thus de$crib'd, it will be requi$ite to adde, that $omething is wont to be done before it be $et on work, for the more ea$ie moving of the Sucker, and for the better exclu$ion of the outward Air: which when the Ve$$el begins to be exhau$ted, is much more dif- ficult to be kept out then one would ea$i- ly imagine. <p>There mu$t then be fir$t powr'd in at the top of the Receiver a little $allad oyl, partly to fill up any $mall intervalls that <pb n=15> may happen to be betwixt the contigu- ous $urfaces of the internal parts of the Stop-cock: And partly that it may be the more ea$ie to turn the Key (S) back- wards and forwards. Pretty $tore of oyl mu$t al$o be pour'd into the Cylindre, both that the Sucker may $lip up and down in it the more $moothly and freely, and that the Air might be the better hindred from getting in between them: And for the like rea$ons, a little oyl is to be u$ed al$o about the Valve. Upon which occa$ion, it would not be omitted (for it is $trange) that oftentimes, when neither the pouring in of water, nor even of oyl alone, prov'd capable to make the Sucker move ea$ily enough in the Cylin- der; a mixture of both tho$e Liquors would readily ($ometimes even to admi- ration) perform the de$ired effect. And la$tly, the bra$s cover of the Receiver, being put into the bra$s ring formerly de- $crib'd, that no Air may get between them, it will be very requi$ite to plai$ter over very carefully the upper edges of both, with the plai$ter formerly mention- ed, or $ome other as clo$e, which is to be $pread upon the edges with a hot Iron; that being melted, it may run into and <pb n=16> fill up all the crannies, or other little ca- vities, at which the Air might otherwi$e get entrance. <p>All things being thus fitted, and the lower $hank (O) of the $top-cock being put into the upper Orifice of the Cylin- der (&), into which it was exactly ground; the Experimenter is fir$t, by turning the handle, to force the Sucker to the top of the Cylinder, that there may be no Air left in the upper part of it: Then $hut- ting the Valve with the Plug, and turning the other way, he is to draw down the Sucker to the bottom of the Cylinder; by which motion of the Sucker, the Air that was formerly in the Cylinder being thru$t out, and none being permitted to $ucceed in its room, 'tis manife$t that the cavity of the Cylinder mu$t be empty, in reference to the Air: So that if there- upon the Key of the Stop-cock be $o turn'd, as that through the perforation of it, a free pa$$age be opened betwixt the Cylinder and the Receiver, part of the Air formerly contain'd in the Receiver, will nimbly de$cend into the Cylinder. And this Air, being by the turning back of the Key hinder'd from the returning into the Receiver, may, by the opening <pb n=17> of the Valve, and forcing up of the Suck- er to the top of the Cylinder again, be driven out into the open Air. And thus by the repetition of the motion of the Sucker upward and downward, and by op- portunely turning the Key, and $topping the Valve, as occa$ion requires, more or le$s Air may be $uck'd out of the Recei- ver, according to the exigency of the Ex- periment, and the intention of him that makes it. <p>Your Lord$hip will, perhaps, think that I have been unnece$$arily prolix in this fir$t part of my Di$cour$e: But if you had $een how many unexpected difficul- ties we found to keep out the externall Air, even for a little while, when $ome con$iderable part of the internal had been $uckt out; You would peradventure al- low, that I might have $et down more circum$tances then I have, without $et- ting down any, who$e knowledge, he that $hall try the Experiment may not have need of. Which is $o true, that, before we proceed any further, I cannot think it un- $ea$onable to adverti$e Your Lord$hip, that there are two chief $orts of Experi- ments, which we de$ign'd in our Engine to make tryal of: The one, $uch as may <pb n=18> be quickly di$patcht, and therefore may be try'd in our Engine, though it leak a little; becau$e the Air may be fa$ter drawn out, by nimbly plying the Pump, then it can get in at undi$cern'd leaks; I $ay at undi$cern'd leaks, becau$e $uch as are big enough to be di$cover'd can $carce be un- ea$ie to be $topt. The other $ort of Ex- periments con$i$ts of tho$e that require not onely that the internal Air be drawn out of the Receiver, but that it be like- wi$e for a long time kept out of it. Such are the pre$ervation of Animal and o- ther Bodies therein, the germination and growth of Vegetables, and other tryals of $everal $orts, which it is apparent can- not be well made unle$s the external Air can, for a competent while, be excluded: Since even at a very $mall leak there may enough get in, to make the <I>Vacuum</I> $oon loo$e that name; by which I here declare once for all, that I under$tand not a $pace wherein there is no body at all, but $uch as is either altogether, or almo$t totally void of Air. <p>Now this di$tinction of Experiments I thought fit to premi$e to the en$uing Narratives, becau$e upon tryal, we found it $o exceeding (and $carce imaginable) dif- <pb n=19> ficult a matter, to keep out the Air from getting at all in at any imperceptible hole or flaw what$oever, in a Ve$$el immedi- ately $urrounded with the compre$$ed At- mo$phere, that in $pight of all our care and diligence, we never were able totally to exhau$t the Receiver, or keep it when it was almo$t empty, any con$iderable time, from leaking more or le$s: although (as we have lately intimated) by unwearyed quickne$s in plying the Pump, the inter- nall Air can be much fa$ter drawn out then the external can get in, till the Re- ceiver come to be almo$t quite empty. And that's enough to enable men to di$- cover hitherto unob$erved <I>Phænomena</I> of Nature. <p>The Experiments therefore of the fir$t $ort, will, I fear, prove the onely ones wherewith my Avocations will allow me to entertain Your Lord$hip in this Letter. For till your further Commands $hall en- gage me to undertake, by Gods permi$- $ion, $uch an Employment, and more lea- $ure $hall better fit me for it, I know not whether I $hall be in a condition to try what may be done, to enable me to give you $ome account of the other $ort of Experiments al$o. <pb n=20> <p>TO proceed now to the <I>Phænomena,</I> <MARG><I>Experi- ment</I> 1.</MARG> exhibited to us by the Engine above de$cribed; I hold it not unfit to begin with what does con$tantly and regularly offer it $elf to our ob$ervation, as depend- ing upon the Fabrick of the Engine it $elf, and not upon the nature of this or that particular Experiment which 'tis employ- ed to try. <p>Fir$t, Then upon the drawing down of the Sucker, (the Valve being $hut) the Cylindrical $pace, de$erted by the Sucker, is left de void of Air; and therefore, up- on the turning of the Key, the Air con- tained in the Receiver ru$hes into the em- ptyed Cylinder, till the Air in both tho$e Ve$$els be brought to about an equal mea$ure of dilatation. And therefore, upon $hutting the Receiver by returning the Key, if you open the Valve, and force up the Sucker again, you will finde, that after this fir$t ex$uction you will drive out almo$t a whole Cylinder full of Air: But at the following ex$uctions, you will draw le$s and le$s of Air out of the Recei- ver into the Cylinder, becau$e that there will $till remain le$s and le$s Air in the <pb n=21> Receiver it $elf; and con$equently, the Particles of the remaining Air, having more room to extend them$elves in, will le$s pre$s out one another. This you will ea$ily perceive, by finding, that you $till force le$s and le$s Air out of the Cylin- der; $o that when the Receiver is almo$t exhau$ted, you may force up the Sucker almo$t to the top of the Cylinder, be- fore you will need to un$top the Valve to let out any Air: And if at $uch time, the Valve being $hut, you let go the handle of the Pump, you will finde the Sucker for- cibly carryed up to the top of the Cylin- der, by the protru$ion of the external Air; which, being much le$s rarified then that within the Cylinder, mu$t have a more forcible pre$$ure upon the Sucker, then the internal is able to re$i$t: And by this means you may know how far you have emptyed the Receiver. And to this we may adde, on this occa$ion, that con$tant- ly upon the turning of the Key to let out the Air from the Receiver, into the em- ptied Cylinder, there is immediately pro- duced a con$iderably brisk noi$e, e$peci- ally whil'$t there is any plenty of Air in the Receiver. <pb n=22> <p>For the more ea$ie under$tanding of the Experiments tryable by our Engine, I thought it not $uperfluous, nor un$ea$on- able in the recital of this fir$t of them, to in$inuate that notion by which it $eems likely that mo$t, if not all, of them will prove explicable. Your Lord$hip will ea$ily $uppo$e, that the Notion I $peak of is, That there is a Spring, or Ela$ti- cal power in the Air we live in. By which <G>e)latg\r</G> or Spring of the Air, that which I mean is this: That our Air either con- $i$ts of, or at lea$t abounds with, parts of $uch a nature, that in ca$e they be bent or compre$$'d by the weight of the incum- bent part of the Atmo$phere, or by any o- ther Body, they do endeavor, as much as in them lies, to free them$elves from that pre$$ure, by bearing again$t the contigu- ous Bodies that keep them bent; and, a$$oon as tho$e Bodies are remov'd or reduced to give them way, by pre$ently unbending and $tretching out them$elves, either quite, or $o far forth as the con- tiguous Bodies that re$i$t them will per- mit, and thereby expanding the whole parcel of Air, the$e ela$tical Bodies com- po$e. <pb n=23> <p>This Notion may perhaps be $ome- what further explain'd, by conceiving the Air near the Earth to be $uch a heap of little Bodies, lying one upon another, as may be re$embled to a Fleece of Wooll. For this (to omit other likene$$es betwixt them) con$i$ts of many $lender and flexi- ble Hairs; each of which, may indeed, like a little Spring, be ea$ily bent or roul- ed up; but will al$o, like a Spring, be $till endeavouring to $tretch it $elf out again. For though both the$e Haires, and the Aerial Corpu$cles to which we liken them, do ea$ily yield to externall pre$$ures; yet each of them (by vertue of its $tructure) is endow'd with a Power or Principle of $elf-Dilatation; by vertue whereof, though the hairs may by a Mans hand be bent and crouded clo$er together, and into a narrower room then $uits be$t with the nature of the Body: Yet whil'$t the compre$$ion la$ts, there is in the fleece they compo$e an endeavour outwards, whereby it continually thru$ts again$t the hand that oppo$es its Expan$ion. And upon the removall of the external pre$- $ure, by opening the hand more or le$s, the compre$$ed Wooll does, as it were, $pon- taneou$ly expand or di$play it $elf towards <pb n=24> the recovery of its former more loo$e and free condition, till the Fleece have ei- ther regain'd its former Dimen$ions, or at lea$t, approach'd them as near as the compre$$ing hand (perchance not quite open'd) will permit. This Power of $elf-Dilatation, is $omewhat more con$pi- cuous in a dry Spunge compre$$'d, then in a Fleece of Wooll. But yet we ra- ther cho$e to imploy the latter, on this occa$ion, becau$e it is not like a Spunge, an entire Body, but a number of $len- der and flexible Bodies, loo$ely com- plicated, as the Air it $elf $eems to be. <p>There is yet another way to explicate the Spring of the Air, namely, by $uppo- $ing with that mo$t ingenious Gentleman, Mon$ieur <I>Des Cartes,</I> That the Air is no- thing but a Congeries or heap of $mall and (for the mo$t part) of flexible Parti- cles; of $everal $izes, and of all kinde of Fi- gures which are rai$'d by heat (e$pecially that of the Sun) into that fluid and $ubtle Etheriall Body that $urrounds the Earth; and by the re$tle$$e agi- tation of that Cele$tial Matter where- in tho$e Particles $wim, are $o whirl'd <pb n=25> round, that each Corpu$cle endeavours to beat off all others from coming within the little Sphear requi$ite to its motion about its own Center; and (in ca$e any, by intruding into that Sphear $hall op- po$e its free Rotation) to expell or drive it away: So that according to this Do- ctrine, it imports very little, whether the particles of the Air have the $tructure re- qui$ite to Springs, or be of any other form (how irregular $oever) $ince their Ela$tical power is not made to depend upon their $hape or $tructure, but upon the vehement agitation, and (as it were) brandi$hing motion, which they receive from the fluid <I>Ether</I> that $wiftly flows between them, and whirling about each of them (independently from the re$t) not onely keeps tho$e $lender Aërial Bodies $eparated and $tretcht out (at lea$t, as far as the Neighbouring ones will per- mit) which otherwi$e, by rea$on of their flexiblene$s and weight, would flag or curl; but al$o makes them hit again$t, and knock away each other, and con$equently require more room, then that which if they were compre$$'d, they would take up. <pb n=26> <p>By the$e two differing ways, my Lord, may the Spring of the Air be explicated. But though the former of them be that, which by rea$on of its $eeming $omewhat more ea$ie, I $hall for the mo$t part make u$e of in the following Di$cour$e: yet am I not willing to declare peremptorily for either of them, again$t the other. And indeed, though I have in another Treati$e endeavoured to make it probable, that the returning of Ela$tical Bodies (if I may $o call them) forcibly bent, to their former po$ition, may be Mechanically explica- ted: Yet I mu$t confe$s, that to deter- mine whether the motion of Re$titution in Bodies, proceed from this, That the parts of a Body of a peculiar Structure are put into motion by the bending of the $pring, or from the endeavor of $ome $ub- tle ambient Body, who$e pa$$age may be oppo$'d or ob$tructed, or el$e it's pre$$ure unequally re$i$ted by rea$on of the new $hape or magnitude, which the bending of a Spring may give the Pores of it: To determine this, I $ay, $eems to me a mat- ter of more difficulty, then at fir$t $ight one would ea$ily imagine it. Wherefore I $hall decline medling with a $ubject, which is much more hard to be explica- <pb n=27> ted, then nece$$ary to be $o, by him, who$e bu$ine$s it is not, in this Letter, to a$$ign the adequate cau$e of the Spring of the Air, but onely to manife$t, That the Air has a Spring, and to relate $ome of its effects. <p>I know not whether I need annex that, though either of the above-mention'd Hypothe$es, and perhaps $ome others, may afford us an account plau$ible enough of the Air-$pring; yet I doubt, whether any of them gives us a $ufficient account of its Nature. And of this doubt, I might here mention $ome Rea$ons, but that, peradventure, I may (God permit- ting) have a fitter occa$ion to $ay $ome- thing of it el$ewhere. And therefore I $hould now proceed to the next Experi- ment, but that I think it requi$ite, fir$t, to $ugge$t to your Lord$hip what comes into my thoughts, by way of An$wer to a plau$ible Objection, which I fore$ee you may make again$t our propo$'d Doctrine, touching the Spring of the Air. For it may be alleadged, that though the Air were granted to con$i$t of Springy Par- ticles (if I may $o $peak) yet thereby we could onely give an account of the Dilatation of the Air in Wine-Guns and <pb n=28> other pneumatical Engines wherein the Air has been compre$$'d, and its Springs violently bent by an apparent externall force; upon the removall of which, 'tis no wonder that the Air $hould, by the motion of re$titution, expand it $elf till it have recovered its more natural dimen- $ions: whereas in our above-mentioned fir$t Experiment, and in almo$t all others tryable in our Engine, it appears not that any compre$$ion of the Air prece- ded its $pontaneous Dilatation or Expan- $ion of it $elf. To remove this difficul- ty, I mu$t de$ire Your Lord$hip to take notice, that of whatever nature the Air, very remote from the Earth, may be, and whatever the Schools may confidently teach to the contrary, yet we have divers Experiments to evince, that the Atmo$- phere we live in is not (otherwi$e then comparatively to more ponderous Bodies) light, but heavy: And did not their gravity hinder them, it appears not why the $teams of the Terraqueous Globe, of which our Air in great part con$i$ts, $hould not ri$e much higher then the Re- fraction of the Sun, and other Stars give men ground to think, that the At- mo$phere, even in the judgement of tho$e <pb n=29> Recent A$tronomers, who $eem willing to enlarge its bounds as much as they dare, does reach. <p>But le$t you $hould expect my $econding this Rea$on by Experience; and le$t you $hould object, That mo$t of the Experi- m&etilde;ts that have been propo$'d to prove the gravity of the Air, have been either barely propo$'d, or perhaps not accuratly try'd; I am content, before I pa$s further, to menti- on here, That I found a dry lambs-bladder containing near about two thirds of a pint, and compre$$'d by a packthred tyed about it, to loo$e a grain and the eighth part of a grain of its former weight, by the rece$s of the Air upon my having prickt it: And this with a pair of Scales, which when the full Bladder and the corre$pondent weight were in it, would manife$tly turn either way with the 32 part of a grain. And if it be further objected, That the Air in the Bladder was violently compre$$'d by the Pack-thred and the $ides of the Bladder, we might probably (to wave prolix an$wers) be furni$h'd with a Re- ply, by $etting down the differing weight of our Receiver, when empty'd and when full of uncompre$$'d Air, if we could here procure $cales fit for $o nice an experiment; <pb n=30> $ince we are informed, that in the <I>German</I> Experiment, commended at the begin- ning of this Letter, the Ingenious Tryers of it found, That their Gla$s Ve$$el, of the capacity of 32 mea$ures, was lighter when the Air had been drawn out of it, then before, by no le$s then one ounce and (3/10) that is, an ounce and very near a third: But of the gravity of the Air, we may el$ewhere have occa$ion to make fur- ther mention. <p>Taking it then for granted that the Air is not deyoid of weight, it will not be unea$ie to conceive, that that part of the Atmo$phere wherein we live, being the lower part of it, the Corpu$cles that com- po$e it, are very much compre$$'d by the weight of all tho$e of the like nature that are directly over them, that is, of all the Particles of Air, that being pil'd up up- on them, reach to the top of the Atmo$- phere. And though the height of this Atmo$phere, according to the famous <I>Kepler,</I> and $ome others, $carce exceeds eight common miles; yet other eminent and later A$tronomers, would promote the confines of the Atmo$phere, to ex- ceed $ix or $even times t<*> number of miles. And the diligent and learned <pb n=31> <I>Riviolo</I> makes it probable, that the At- mo$phere may, at lea$t in divers places, be at lea$t 50 miles high. So that according to a moderate e$timate of the thickne$s of the Atmo$phere, we may well $uppo$e, that a Column of Air, of many miles in height, leaning upon $ome $pringy Cor- pu$cles of Air here below, may have weight enough to bend their little $prings, and keep them bent: As, to re$ume our former compari$on, if there were fleeces of Wooll pil'd up to a mountainous height upon one another, the Hairs that com- po$e the lowermo$t locks which $upport the re$t, would, by the weight of all the Wool above them, be as well $trongly compre$$ed, as if a man $hould $queeze them together in his hands, or imploy any $uch other moderate force to compre$s them. So that we need not wonder, that upon the taking off the incumbent Air from any parcel of the Atmo$phere here below, the Corpu$cles, whereof that un- dermo$t Air con$i$ts, $hould di$play them- $elves, and take up more room then be- fore. <p>And if it be objected, That in Water, the weight of the upper and of the lower part is the $ame: I an$wer, That be$ides <pb n=32> that it may be well doubted whether the ob$ervation, by rea$on of the great diffi- culty have been exactly made, there is a manife$t di$parity betwixt the Air and Water: For I have not found, that upon an Experiment purpo$ely made, (and in another Treati$e Recorded) that Water will $uffer any con$iderable compre$$ion; whereas we may ob$erve in Wind-Guns (to mention now no other Engines) that the Air will $uffer it $elf to be crouded in- to a comparatively very little room; in $o much, that a very diligent Examiner of the <I>Phænomena</I> of Wind-Guns would have us believe, that in one of them, by conden$ation, he reduc'd the Air into a $pace at lea$t eight times narrower then it before po$$e$t. And to this, if we adde a noble <I>Phænomenon</I> of the Experiment <I>De Vacuo;</I> the$e things put together, may for the pre$ent $uffice to countenance our Doctrine. For that noble Experimenter, Mon$ieur <I>Pa$cal</I> (the Son) had the com- mendable Curio$ity to cau$e the <I>Torri- cellian</I> Experiment to be try'd at the foot, about the middle, and at the top of that high Mountain (in <I>Auvergne,</I> if I mi$take not) commonly call'd <I>Le Puy de Domme;</I> whereby it was found, That the <I>Mercury</I> <pb n=33> in the Tube fell down lower, about three inches, at the top of the Mountain then at the bottom. And a Learned Man a while $ince inform'd me, That a great <I>Virtuo$o,</I> friend to us both, has, with not unlike $ucce$s, tryed the $ame Experi- ment in the lower and upper parts of a Mountain in the We$t of <I>England:</I> Of which, the rea$on $eems manife$tly enough to be this, That upon the tops of high Mountains, the Air which bears again$t the re$tagnant Quick-$ilver, is le$s pre$$'d by the le$s ponderous incumbent Air; and con$equently is not able totally to hinder the de$cent of $o tall and heavy a Cylin- der of Quick-$ilver, as at the bottom of $uch Mountains did but maintain an <I>Æqui- librium</I> with the incumbent Atmo$phere. <p>And if it be yet further Objected a- gain$t what hath been propo$'d touching the compactne$s and pre$$ure of the Infe- rior Air; That we finde this very Air to yield readily to the motion of little Flies, and even to that of Feathers, and $uch o- ther light and weak Bodies; which $eems to argue, that the particles of our Air are not $o compre$$'d as we have repre$ented them, e$pecially, $ince by our former Experiment it appears, that the Air rea- <pb n=34> dily dilated it $elf downward, from the Receiver into the Pump, when 'tis plain, that it is not the incumbent Atmo$phere, but onely the $ubjacent Air in the bra$s Cylinder that has been remov'd: If this, I $ay, be objected, we may reply, That when a man $queezes a Fleece of Wool in his hand, he may feel that the Wool in- ce$$antly bears again$t his hand, as that which hinders the hairs it con$i$ts of, to recover their former and more natural ex- tent. So each parcel of the Air about the Earth, does con$tantly endeavour to thru$t away all tho$e contiguous Bodies, whe- ther Aërial or more gro$s, that keep them bent, and hinder the expan$ion of its parts, which will dilate them$elves or flie abroad towards that part, whether up- wards or downwards, where they finde their attempted Dilatation of them$elves le$s re$i$ted by the neihgboring Bodies. Thus the Corpu$cles of that Air we have been all this while $peaking of, being un- able, by rea$on of their weight, to a$cend above the Convexity of the Atmo$phere, and by rea$on of the re$i$tance of the $ur- face of the Earth and Water, to fall down lower, they are forced, by their own gra- vity and this re$i$tance, to expand and <pb n=35> diffu$e them$elves about the Terre$tial Globe; whereby it comes to pa$s, that they mu$t as well pre$s the contiguous Corpu$cles of Air that on either $ide op- po$e their Dilatation, as they mu$t pre$s upon the $urface of the Earth, and, as it were recoyling thence, endeavor to thru$t away tho$e upper particles of Air that lean upon them. <p>And as for the ea$ie yielding of the Air to the Bodies that move in it, if we con- $ider that the Corpu$cles whereof it con- $i$ts, though of a $pringy nature, are yet $o very $mall, as to make up (which 'tis manife$t they doe) a fluid Body, it will not be difficult to conceive, that in the Air, as in other Bodies that are fluid, the little Bodies it con$i$ts of are in an almo$t re$tle$s motion, whereby they become (as we have more fully di$cour$ed in ano- <MARG><I>In a Di$- cour$e touching $luidity and firm- ne$s.</I></MARG> ther Treati$e) very much di$po$ed to yield to other Bodies, or ea$ie to be di$- plac'd by them, and that the $ame Cor- pu$cles are likewi$e $o variou$ly mov'd, as they are intire Corpu$cles, that if $ome $trive to pu$h a Body plac'd among them towards the right hand (for in$tance) others, who$e motion has an oppo$ite de- termination, as $trongly thru$t the $ame <pb n=36> Body towards the left; whereby neither of them proves able to move it out of its place, the pre$$ure on all hands being reduced as it were to an <I>Æquilibrium:</I> $o that the Corpu$cles of the Air mu$t be as well $ometimes con$idered under the no- tion of little Springs, which remaining bent, are in their entire bulk tran$ported from place to place; as under the notion of Springs di$playing them$elves, who$e parts flie abroad whil$t as to their entire bulk they $carce change place: As the two ends of a Bow, $hot off, fly from one another, whereas the Bow it $elf may be held fa$t in the Archers hand; and that it is the equal pre$$ure of the Air on all $ides upon the Bodies that are in it, which cau- $es the ea$ie Ce$$ion of its parts, may be argu'd from hence: That if by the help of our Engine the Air be but in great part, though not totally drawn away from one $ide of a Body without being drawn away from the other; he that $hall think to move that Body too and fro, as ea$ily as before, will finde him$elf much mi$taken. <p>In verification of which we will, to di- vert your Lord$hip a little, mention here a <I>Phænomenon</I> of our Engine, which even <pb n=37> to divers ingenious per$ons has at fir$t $ight $eem'd very wonderful. <p>THe thing that is wont to be admired, <MARG><I>Experi- ment</I> 2.</MARG> and which may pa$s for our $econd Experiment is this, That if, when the Receiver is almo$t empty, a By-$tander be de$ired to lift up the bra$s Key (former- ly de$cribed as a $topple in the bra$s Co- ver) he will finde it a very difficult thing to do $o, if the Ve$$el be well exhau$ted; and even when but a moderate quantity of Air has been drawn out, he will, when he has lifted it up a little, $o that it is $ome- what loo$e from the $ides of the lip or $ocket, which (with the help of a little oyl) it exactly filled before, he will (I $ay) finde it $o difficult to be lifted up, that he will imagine there is $ome great weight fa$tned to the bottom of it. And if (as $ometimes has been done for merriment) onely a Bladder be tyed to it, it is plea- $ant to $ee how men will marvail that $o light a Body, filled at mo$t but with Air, $hould $o forcibly draw down their hand as if it were fill'd with $ome very ponder- ous thing: whereas the cau$e of this pret- ty <I>Phænomenon</I> $eems plainly enough to <pb n=38> be onely this, That the Air in the Recei- ver, being very much dilated, its Spring mu$t be very much weakn'd, and con$e- quently it can but faintly pre$s up the lower end of the $topple, whereas the Spring of the external Air being no way debilitated, he that a little lifts up the $topple mu$t with his hand $upport a pre$- $ure equal to the di$proportion betwixt the force of the internal expanded Air, and that of the Atmo$phere incumbent upon the upper part of the $ame key or $topple: And $o men being unu$'d to finde any re- $i$tance, in lifting things up, from the free Air above them, they are forward to conclude that that which depre$$es their hands mu$t needs be $ome weight, though they know not where plac'd, drawing be- neath it. <p>And that we have not mi$-a$$ign'd the cau$e of this <I>Phænomenon</I> $eems evident enough by this; That as Air is $uffer- ed by little and little to get into the Re- ceiver, the weight that a man fancies his hand $upports is manife$tly felt to decrea$e more and more, the internal Air by this recruit approaching more to an <I>Æquili- brium</I> with the external, till at length the Receiver growing again full of Air, the <pb n=39> $topple may be lifted up without any dif- ficulty at all. <p>By $everal other of the Experiments afforded us by our Engine, the $ame no- tion of the great and equal pre$$ure of the free Air upon the Bodies it environs, might be here manife$ted, but that we think it not $o fit to anticipate $uch Ex- periments: And therefore $hall rather employ a few lines to clear up a difficulty touching this matter, which we have ob- $erv'd to have troubled $ome even of the Philo$ophical and Mathematical Specta- tors of our Engine, who have wonder'd that we $hould talk of the Air exqui$itely $hut up in our Receiver, as if it were all one with the pre$$ure of the Atmo$phere; whereas the thick and clo$e body of the Gla$s, wholly impervious to the Air, does manife$tly keep the incumbent Pillar of the Atmo$phere from pre$$ing in the lea$t upon the Air within the Gla$s, which it can no where come to touch. To eluci- date a little this matter, let us con$ider, That if a man $hould take a fleece of Wool, and having fir$t by compre$$ing it in his hand reduc'd it into a narrower com- pa$s, $hould nimbly convey and $hut it clo$e up into a Box ju$t fit for it, though <pb n=40> the force of his hand would then no lon- ger bend tho$e numerous $pringy Body's that compo$e the Fleece, yet they would continue as $trongly bent as before, be- cau$e the Box they are inclo$'d in would as much re$i$t their re-expanding of them$elves, as did the hand that put them in. For thus we may conceive, that the Air being $hut up, when its parts are bent by the whole weight of the incumbent Atmo$phere, though that weight can no longer lean upon it, by rea$on it is kept off by the Gla$s, yet the Corpu$cles of the Air within that Gla$s continue as forcibly bent as they were before their in- clu$ion, becau$e the $ides of the Gla$s hinder them from di$playing or $tretch- ing out them$elves. And if it be ob- jected that this is unlikely, becau$e ev'n Gla$s bubles, $uch as are wont to be blown at the flame of a Lamp, exceeding thin and Hermetically $eal'd will not break; whereas it cannot be imagin'd that $o thin a Pri$on of Gla$s could re- $i$t the Ela$tical force of all the included Air, if that Air were $o compre$$'d as we $uppo$e. It may be ea$ily reply'd, That the pre$$ure of the inward Air again$t the Gla$s, is countervail'd by the equal pre$- <pb n=41> $ure of the outward again$t the $ame Gla$s. And we $ee in bubles, that by rea$on of this an exceeding thin film of Water is often able, for a good while, to hinder the eruption of a pretty quantity of Air. And this may be al$o more con$picuous in tho$e great Spherical bubles that boyes $ometimes blow with Water, to which Sope has given a Tenacity. But that, if the pre$$ure of the ambient Air were remov'd, the internal Air may be able to break thicker Gla$$es then tho$e lately men- tion'd, will appear by $ome of the follow- ing Experiments; to which we $hall there- fore now ha$ten, having, I fear, been but too prolix in this Excur$ion, though we thought it not ami$s to annex to our fir$t Experiments $ome general Con$iderati- ons touching the Spring of the Air, be- cau$e (this Doctrine being yet a $tranger to the Schools) not onely we finde not the thing it $elf to be much taken notice of; but of tho$e few that have heard of it, the greater part have been forward to re- ject it, upon a mi$taken Per$wa$ion, that tho$e <I>Phænomena</I> are the effects of natures abhorrency of a <I>Vacuum,</I> which $eem to be more fitly a$cribeable to the weight and Spring of the Air. <pb n=42> <p>WE will now proceed to ob$erve that <MARG><I>Experi- ment</I> 3.</MARG> though, by the help of the handle, the Sucker be ea$ily drawn down to the bottom of the Cylinder; yet, without the help of that Leaver, there would be required to the $ame effect, a force or weight great enough to $urmount the pre$$ure of the whole Atmo$phere: Since otherwi$e the Air would not be driven out of its place, when none is permitted to $ucceed into the place de$erted by the Sucker. This $eems evident, from the known <I>Torricellian</I> Experiment, in which, if the inverted Tube of <I>Mercury</I> be but 25 Digits high, or $omewhat more, the Quick-$ilver will not fall but remain $u$- pended in the Tube; becau$e it cannot pre$s the $ubjacent <I>Mercury</I> with $o great a force, as does the incumbent Cylinder of the Air reaching thence to the top of the Atmo$phere: Whereas, if the Cy- linder of <I>Mercury</I> were three or four digits longer, it would over-power that of the external Air, and run out into the Ve$$el'd <I>Mercury,</I> till the two Cylinders came to an <I>Æquilibrium,</I> and no further. Hence we need not wonder, that though the <pb n=43> Sucker move ea$ily enough up and down in the Cylinder by the help of the <I>Manu- brium;</I> yet if the <I>Manubrium</I> be taken off, it will require & con$iderable $trength to move it either way. Nor will it $eem $trange, that if, when the Valve and Stop-cock are well $hut, you draw down the Sucker, and then let go the <I>Manubri- um;</I> the Sucker will, as it were of it $elf, re-a$cend to the top of the Cylinder, $ince the $pring of the external Air findes no- thing to re$i$t its pre$$ing up the Sucker. And for the $ame rea$on, when the Re- ceiver is almo$t evacuated, though, ha- ving drawn down the Sucker, you open the way from the Receiver to the Cylin- der, and then intercept that way again by returning the Key; the Sucker will, up- on the letting go the <I>Manubrium,</I> be forcibly carried up almo$t to the top of the Cylinder: Becau$e the Air within the Cylinder, being equally dilated and weak- ned with that of the Gla$s, is unable to with$tand the pre$$ure of the external Air, till it be driven into $o little $pace, that there is an <I>Æquilibrium</I> betwixt its force and that of the Air without. And con- gruou$ly hereunto we finde, that in this ca$e, the Sucker is drawn down with little <pb n=44> le$s difficulty, then if the Cylinder, be- ing devoid of Air, the Stop-cock were exactly $hut: We might take notice of $ome other things, that depend upon the Fabrick of our Engine it $elf; but to $hun prolixity, we will, in this place, content our $elves to mention one of them, which $eems to be of greater moment then the re$t, and it is this; that when the Sucker has been impell'd to the top of the Cylin- der, and the Valve is $o carefully $topp'd, that there is no Air left in the Cylinder a- bove the Sucker: If then the Sucker be drawn to the lower part of the Cylinder, he that manages the Pump findes not any $en$ibly greater difficulty to depre$s the Sucker, when it is nearer the bottom of the Cylinder, then when it is much further off. Which circum$tance we therefore think fit to take notice of, becau$e an eminent Mo- dern Naturali$t hath taught, that, when the Air is $ucked out of a Body, the violence wherewith it is wont to ru$h into it again, as $oon as it is allow'd to re-enter, pro- ceeds mainly from this; That the pre$$ure of the ambient Air is $trengthned upon the acce$$ion of the Air $uck'd out; which, to make it $elf room, forces the neighbor- ing Air to a violent-$ubingre$$ion o$ its parts: which, i$ it were true, he that draws <pb n=45> down the Sucker, would finde the re$i$t- ance of the external Air increa$'d as he draws it lower, more of the di$placed Air being thru$t into it to compre$s it. But, by what has been di$cour$'d upon the fir$t Experiment, it $eems more probable, that without any $uch $trengthning of the pre$- $ure of the outward Air, the taking quite away or the debilitating of the re$i$tance from within, may $uffice to produce the effects under con$ideration. But this will perhaps be illu$trated by $ome or other of our future Experiments, and therefore $hall be no longer in$i$ted on here. <p>HAving thus taken notice of $ome of <MARG><I>Experi- ment</I> 4.</MARG> the con$tant <I>Phænomena</I> of our En- gine it $elf, let us now proceed to the Ex- periments tryable in it. <p>We took then a Lambs Bladder large, well dry'd, and very limber, and leaving in it about half as much Air as it could con- tain, we cau$'d the neck of it to be $trong- ly ty'd, $o that none of the included Air, though by pre$$ure, could get out. This Bladder being convey'd into the Receiver, and the Cover luted on, the Pump was $et awork, and after two or three ex$uctions of the ambient Air (where- by the Spring of that which remain'd in <pb n=46> the Gla$s was weaken'd) the Impri$on'd Air began to $well in the Bladder, and as more and more of the Air in the Recei- ver was, from time to time, drawn out; $o did that in the Bladder more and more ex- pand it $elf, and di$play the folds of the formerly flaccid Bladder: $o that before we had exhau$ted the Receiver near $o much as we could, the Bladder appear'd as full and $tretched, as if it had been blown up with a Quill. <p>And that it may appear that this plump- ne$s of the Bladder proceeded from the $urmounting of the debilitated Spring of the ambient Air remaining in the Ve$$el, by the $tronger Spring of the Air remain- ing in the Bladder; we Return'd the Key of the Stop-cock, and by degrees allow'd the external Air to return into the Recei- ver: Whereupon it happen'd, as was ex- pected, that as the Air came in from with- out, the di$turb'd Air in the Bladder, was proportionably compre$$'d into a narrow- er room, and the $ides of the Bladder grew flaccid, till the Receiver having re- admitted its wonted quantity of Air, the Bladder appear'd as full of wrinkles and cavities as before. <pb n=47> <p>This Experiment is much of the $ame nature with that which was $ome years agoe $aid to be made by that eminent Ge- ometrician Mon$ieur <I>Roberval,</I> with a Carps Bladder empty'd and convey'd into a Tube, wherein the Experiment <I>De Va- cuo</I> was afterwards try'd, which ingeni- ous Experiment of his ju$tly de$erves the thanks of tho$e that have been, or $hall be $olicitous to di$cover the nature of the Air. <p>But to return to our Experiment, we may take notice of this Circum$tance in it, That after the Receiver has been in $ome mea$ure empty'd, the Bladder do's, at each ex$uction, $well much more con- $picuou$ly then it did at any of the fir$t Ex$uctions; in$omuch that towards the end of the pumping, not onely a great fold or cavity in the $urface of the Blad- der may be made, even by the $tretching of the inward $elf-expanding Air: But we have $ometimes $een, upon the turn- ing of the Key to let the ambient Air pa$s out of the Receiver into the Cylin- der, we have $een (I $ay) the Air in the Bladder $uddenly expand it $elf $o much and $o briskly, that it manife$tly lifted up $ome light Bodies that lean'd upon it, <pb n=48> and $eem'd to lift up the Bladder it $elf. <p>Now becau$e it has by very Learned Men been doubted whether the $welling of the Bladder may not have proceeded from the Dilatation of the included Air, but from the Texture of the Fibres, which, being wont to keep the Bladder extended when the Animal to whom it belong'd was alive, may be $uppo$'d in our Experiment to have return'd, like $o many Springs to their wonted extent, up- on the removal of the Ambient Air that compre$$'d and bent them: becau$e this, I $ay, has been doubted, we thought fit to make this further tryall. <p>We let down into the Receiver with the fore-mentioned Bladder two other much $maller, and of the $ame kinde of Animal; the one of the$e was not ty'd up at the neck that there might be liberty left to the Air that was not $queez'd out (which might amount to about a fifth part of what the Bladder held before) to pa$s out into the Receiver: The other had the $ides of it $tretch'd out and pre$$'d to- gether, almo$t into the form of a Cup, that they might intercept the le$s Air be- twixt them, and then was $trongly ty'd <pb n=49> up at the neck: This done, and the Air being in $ome mea$ure $uck'd out of the Pneumatical Gla$s (if I may $o call it) the Bladder, mention'd at the beginning of our Experiment, appear'd extended e- very way to its full Dimen$ions; whereas neither of the two others did remarkably $well, and that who$e neck was not ty'd $eem'd very little, if at all le$s wrinkl'd then when it was put in. <p>We made likewi$e a $trong Ligature a- bout the middle of a long Bladder part- ly empty'd, and upon the drawing the Air out of the Receiver, could ob$erve no $uch $welling betwixt the Ligature and the Neck of the Bladder, which had been purpo$ely left open, as betwixt the $ame Ligature and the bottom of the Bladder, whence the included Air could no way get out. <p>But a further and $ufficient manife$tati- on whence the intume$$ence of the Blad- der proceeds, may be deduc'd from the following Experiment. <p>TO try then at once both what it was <MARG><I>Experi- ment</I> 5.</MARG> that expanded the Bladder, and what a powerful Spring there is ev'n in the Air <pb n=50> we are wont to think uncompre$$'d, we cau$'d a Bladder dry, well ty'd and blown moderately full, to be hung in the Recei- ver by one end of a $tring, who$e other end was fa$tned to the in$ide of the Co- ver: and upon drawing out the ambient Air, that pre$$'d on the Bladder; the in- ternal Air not finding the wonted re$i$t- ance, fir$t $well'd and di$tended the Blad- der, and then broke it, with $o wide and crooked a rent, as if it had been forcibly torn a$$under with hands. After which a $econd Bladder being convey'd in, the Ex- periment was repeated with like $ucce$s: And I $uppo$e it will not be imagin'd that in this ca$e the Bladder was broken by its own Fibres, rather then by the Impri- $on'd Air. <p>And of this Experiment the$e two <I>Phæ- nomena</I> may be taken notice of: The one, that the Bladder at its breaking gave a great report, almo$t like a Craker: And the other, That the Air contain'd in the Bladder, had the power to break it with the mention'd Impetuo$ity, long before the ambient Air was, all or near all, drawn out of the Receiver. <p>But, to verifie what we $ay in another Di$cour$e, where we $how, That even <pb n=51> true Experiments may, by rea$on of the ea$ie mi$take of $ome unheeded Circum$tance, be un$ucce$sfully try'd; we will Adverti$e, on this occa$ion, that we did oftentimes in vain try the breaking of Bladders, after the manner above-mention'd: Of which the cau$e appear'd to be this, That the Bladders we could not break, having been brought us ready blown from tho$e that $old them, were grown dry before they came to our hands: whence it came to pa$s, that, if we afterwards ty'd them very hard, they were apt to fret and $o become un$ervice- able; and if we ty'd them but moderate- ly hard, their $tiffne$s kept them from be- ing clo$'d $o exactly, but that when the included Air had in the exhau$ted Recei- ver di$tended them as much as ea$ily it could, it would in part get out between the little wrinkles of the Sphincter of the Neck: Whence al$o it u$ually happen'd, that, upon the letting in the Air from without, the Bladders appear'd more flac- cid and empty then before they were put in; whereas when the Bladders were brought us moi$t from the Butchers, we could, without injuring them, tye their necks $o clo$e, that none of the Air once <pb n=52> blown in, could get out of them, but by violently breaking them. <p>It will not be ami$s on this occa$ion to point at $omething which may de$erve a more deliberate Speculation then we can now afford it; namely that the Ela$tical Power of the $ame Quantity of Air may be as well Encrea$'d by the Agitation of the Aërial Particles (whether onely mo- ving them more $wiftly and $cattering them, or al$o extending or $tretching them out, I determine not) within an every way inclo$ing and yet yielding Bo- dy; as Di$play'd by the withdrawing of the Air that pre$$'d it without. For we found that a Bladder, but moderately fill'd with Air and $trongly ty'd, being a while held near the Fire, not onely grew exceeding turgid and hard, but after- wards, being approach'd nearer to the Fire, $uddenly broke with $o loud and ve- hement a noi$e, as $tony'd tho$e that were by, and made us, for a while after, almo$t deaf. <p>HAving thus $een that the Air has an <MARG><I>Experi- ment</I> 6.</MARG> Ela$tical Power, we were next de$i- rous to know in $ome mea$ure how far a <pb n=53> parcel of Air might by this its own Spring be dilated. And though we were not pro- vided of In$truments fit to mea$ure the dilatation of the Air any thing accurately, yet becau$e an imperfect mea$ure of it was more de$ireable then none at all, we de- vi$'d the following Method as very ea$ily practicable. <p>We took a limber Lambs Bladder which was thorowly wetted in fair Water, that the $ides of it being $queez'd roge- ther, there might be no Air left in its folds: (as indeed we could not afterwards upon tryal di$cern any) The neck of this Bladder was $trongly tyed about that of a $mall Gla$s, (capable of holding five full drachmes of Water) the Bladder be- ing fir$t $o compre$$'d, that all the inclu- ded Air was onely in the Gla$s, without being pre$$'d there; then the Pump be- ing $et awork after a few ex$uctions, the Air in the little Viol began to dilate it $elf and produce a $mall Tumor in the Neck of the Bladder; and as the ambi- ent Air was more and more drawn away, $o the included Air penetrated further and further into the Bladder, and by degrees lifted up the $ides and di$play'd its folds, till at length it $eem'd to have blown it <pb n=54> up to its full extent: whereupon the ex- ternal Air, being permitted to flow back into the Reciver, repul$'d the Air that had fill'd the Bladder into its former nar- row receptacle, and brought the Bladder to be again flaccid and wrinkled as before: Then taking out the Bladder, but with- out $evering it from the Gla$s, we did by a hole made at the top of the Bladder fill the Ve$$el they both made up with Wa- ter, who$e weight was five Ounces five Drachmes and an half: Five Drachmes whereof were above-mention'd to be the contents of the Bottle. So that in this Ex- periment, when the Air had mo$t extend- ed the Bladder, it po$$e$$'d in all above nine times as much room as it did when it was put into the Receiver. And it would probably have much inlarg'd its bounds, but that the Bladder by its weight and the $ticking together of its $ides did $ome- what re$i$t its expan$ion: And which was more con$iderable, the Bladder appear'd tumid enough, whil$t yet a pretty deal of Air was left in the Receiver, who$e ex- $uction would, according to our former Ob$ervation, probably have given way to a further expan$ion of the Air, e$peci- <pb n=55> ally $uppo$ing the dilatation not to be re- $train'd by the Bladder. <p>SInce we wrote the other day the former Experiment, we have met with $ome Gla$$es not very unfit for our purpo$e; by means of which we are now able, with a little more trouble, to mea$ure the ex- pan$ion of the Air a great deal more ac- curately then we could by the help of the above-mention'd Bladder, which was much to narrow to allow the Air its ut- mo$t di$tention. <p>We took then fir$t a Cylindrical Pipe of Gla$s, who$e bore was about a quarter of an Inch in Diameter: this Pipe was $o bent and doubled, that, notwith$tanding its being about two foot in length, it might have been $hut up into a $mall Re- ceiver, not a Foot high: But by mi$- fortune it crack'd in the cooling, whereby we were reduced to make u$e of one part which was $traight and intire, but exceed- ed not $ix or $even Inches. This little Tube was open at one end; and at the other, where it was Hermetically $eal'd, had a $mall Gla$s bubble to receive the Air who$e dilatation was to be mea$ur'd. <pb n=56> <p>Along the $ide of this Tube was pa$t- ed a $traight narrow piece of Parchment, divided into twenty $ix equal parts, mark- ed with black Lines and Figures, that by them might be mea$ur'd both the inclu- ded Air and its dilatation. Afterwards we fill'd the Tube with Water almo$t to the top, and $topping the open end with a Finger, and inverting the Tube, the Air was permitted to a$cend to the above- mention'd Gla$s bubble. And by rea- $on this a$cent was very $low, it gave us the opportunity to mark how much more or le$s then one of the twenty $ix divi$i- ons this Air took up. By this means, af- ter a tryal or two, we were inabled to con- vey to the top of the Gla$s a bubble of Air equal enough, as to $ight, to one of tho$e Divi$ions: Then the open end of the Tube being put into a $mall Viol, who$e bottom was cover'd with Water about half an Inch high; we included both Gla$$es into a $mall and $lender Re- ceiver, and cau$ed the Pump to be $et a- work. The event was, That at the fir$t ex$uction of the Air there appear'd not any expan$ion of the bubble, comparable to what appear'd at the $econd, and that upon a very few ex$uctions the bubble <pb n=57> reaching as low as the $urface of the $ub- jacent Water, gave us cau$e to think that if our Pipe had not been broken it would have expanded it $elf much fur- ther: Wherefore we took out the little Tube, and found that be$ides the twenty $ix divi$ions formerly mention'd, the Gla$s bubble and $ome part of the Pipe to which the divided Parchment did not reach, amounted to $ix divi$ions more. Whereby it appears that the air had taken up one and thirty times as much room as before, and yet $eem'd capable of a much greater expan$ion, if the Gla$s would have permitted it. Wherefore, after the former manner, we let in another bubble, that by our gue$s was but half as big as the former, and found, that upon the ex- $uction of the Air from the Receiver, this little bubble did not onely fill up the whole Tube, but (in part) break through the $ubjacent Water in the Viol, and thereby manife$t it $elf to have po$$e$$ed $ixty and odde times its former room. <p>The$e two Experiments are mention'd to make way for the more ea$ie belief of that which is now to follow. Finding then that our Tube was too $hort to $erve our turn, we took a $lender Quill of Gla$s <pb n=58> which happen'd to be at hand, though it were not $o fit for our purpo$e as we could have wi$hed, in regard it was three or four times as big at one end as the o- ther. This Pipe which was thirty Inches long, being Hermetically $eal'd at the $lender end, was almo$t filled with Wa- ter; and after the above-related manner a bubble was convey'd to the top of it, and the open extream was put into a Viol that had a little fair Water at the bottom: Then the Cover, by means of a $mall hole purpo$ely made in it for the Gla$s Pipe to $tand out at, was cemented on to the Re- ceiver, and the Pump being $et awork, after $ome ex$uctions, not onely the Air manife$tly appear'd extended below the $urface of the $ubjacent Water; but one of the By-$tanders affirms, that he $aw $ome bubbles come out at the bottom of the Pipe and break through the Water This done, we left off Pumping, and ob- $erv'd how at the unperceiv'd leaks of the Receiver the Air got in $o fa$t, thatit very quickly impell'd up the Water to the top of the Tube, excepting a little $pace whereinto that bubble was repul$'d, which had $o lately po$$e$$'d the whole Tube; this Air at the $lender end ap- <pb n=59> pear'd to be a Cylinder of 5/6 parts of an Inch in length; but when the Pipe was taken out and turn'd up$ide down, it ap- pear'd at the other end inferior in bulk to a Pea. <p>The$e things being thus done we took (to make the Experiment the more ex- actly) a $mall pair of Scales, $uch as Gold- Smiths u$e to weigh Gold Coyn in; and weighing the Tube and Water in it, we found them to amount to one Ounce thir- ty Grains and an half: Then we pour'd in as much Water as $erv'd to fill up the Tube, wherein before we had left as much $pace unfill'd up as was po$$e$$'d by the bubble; and weighing again the Pipe and Water, we found the weight increa$'d onely by one Grain. La$tly, pouring out the Water, and carefully freeing the Pipe from it (which yet we could not perfectly doe) we weighed the Gla$s alone, and found it to want two Drachmes and thirty two Grains of its former weight: So that the bubble of Air taking up the room but of one Grain in weight of Water, it appear'd that the Air by its own <G>e)lith\r</G> was $o rarified, as to take up one hundred fifty two times as much room as it did be- fore: though it were then compre$$'d by <pb n=60> nothing but the ordinary pre$$ure of the contiguous Air. I know not whether it be requi$ite to take notice, that this Ex- periment was made indeed in a moi$t Night, but in a Room, in who$e Chim- ney there was burning a good Fire, which did perhaps $omewhat rarifie the Air of which the bubble con$i$ted. <p>It has $eem'd almo$t incredible which is related by the Indu$trious <I>Mer$ennus,</I> That the Air by the violence of heat, though as great as our Ve$$els can $upport with- out fu$ion, can be $o dilated as to take up $eventy times as much room as before: Wherefore becau$e we were willing to have a confirmation of $o $trange a <I>Phæno- menon;</I> we once more convey'd into the Tube a bubble of the bigne$s of the for- mer, and pro$ecuting the Experiment as before with the $ame Water, we ob$erved that the Air did manife$tly $tretch it $elf $o far, as to appear $everal times a good way below the $urface of the Water in the Viol, and that too with a $urface very convex toward the bottom of the Pipe. Nay, the Pump being ply'd a little lon- ger, the Air did manife$tly reach to that place where the bottom of the Tube lean'd upon the bottom of the Viol, and <pb n=61> $eem'd to knock upon it and rebound from it: Which Circum$tances we adde, partly that the <I>Phænomenon</I> we have been relating may not be imputed to the bare $ub$iding of the Water that fill'd the Tube, upon the taking off the pre$- $ure of the ambient Air. And partly al- $o that it may appear that if our Expe- riments have not been as accurately made as with fitter In$truments might perhaps be po$$ible; yet the expan$ion of the Air is likely to be rather greater then le$$er then we have made it: Since the Air was able to pre$s away the Water at the bottom of the Pipe, though that were about two Inches below the $urface of the Water that was then in the Viol, and would have been at lea$t as high in the Pipe, if the Water had onely $ub$ided and not been depre$$ed: So that it $eems not unlikely that if the Experiment could be $o made, as that the expan$ion of the Air might not be re$i$ted by the Neighboring Bodies, it would yet inlarge its bounds, and perhaps $tretch it $elf to two hundred times its former bulk, if not more. How- ever, what we have now try'd will, I hope, $uffice to hinder divers of the <I>Phænomena</I> of our Engine from being di$tru$ted: <pb n=62> Since in that part of the Atmo$phere we live in, that which we call the free Air (and pre$ume to be $o uncompre$$'d) is crouded into $o very $mall a part of that $pace, which if it were not hindred it would po$- $e$s. We would gladly have tryed al$o whether the Air at its greate$t expan$ion could be further rarified by heat; but do what we could, our Receiver leak'd too fa$t to let us give our $elves any $atisfacti- on in that particular. <p>TO di$cover likewi$e by the means of <MARG><I>Experi- ment</I> 7.</MARG> that pre$$ure of the Air, both the $trength of Gla$s, and how much inte- re$t the Figure of a Body may have in its greater or le$$er Re$i$tance to the pre$$ure of other Bodys, we made the$e further tryals. <p>We cau$'d to be blown with a Lamp a round Gla$s bubble, capable of contain- ing, by gue$s, about five Ounces of Wa- ter, with a $lender neck about the bigne$s of a Swans Quill, and it was purpo$ely blown very thin, as Viols made with Lamps are wont to be, that the thinne$s of the matter might keep the roundne$s of the Figure from making the Ve$$el too <pb n=63> $trong. Then having moderately empty- ed the Receiver, and taken it out of the Pump, we $peedily applyed to the Ori- fice of the bottom of it the Neck of the newly mention'd Gla$s, carefully $topping the Crannys with melted Plai$ter, that no Air might get in at them: And after turning the Key of the Stop-cock, we made a free pa$$age for the Air to pa$s out of the bubble into the Receiver: which it did with great celerity, leaving the bub- ble as empty as the Receiver it $elf; as ap- pear'd to us by $ome Circum$tances not now to be in$i$ted on. Notwith$tanding all which, the Ve$$el, continuing as intire as before, gave us cau$e to wonder that the bare Roundne$s of the Figure $hould inable a Gla$s, almo$t as thin as Paper, to re$i$t $o great a pre$$ure as that of the whole incumbent Atmo$phere. And ha- ving reiterated the Experiment, we found again that the pre$$ure of the ambient Body, thru$ting all the parts inwards, made them, by rea$on of their arched Fi- gure, $o $upport one another, that the Gla$s remain'd as whole as at fir$t. <p>Now that the Figure of the Gla$s is of great moment in this matter, may be evinced by this other Experiment. <pb n=64> <p>WE took a Gla$s Helmet or Alem- <MARG><I>Experi- ment</I> 8.</MARG> bick (delineated by the $eventh Figure) $uch as Chymi$ts u$e in Di$tilla- tions, and containing by conjecture be- tween two and three Pints: The <I>Ro$trum</I> or No$e of it mark'd with <I>(c)</I> was Herme- tically clo$ed; and at the top of it was a hole, into which was fitted and cemented one of the Shanks of a middle-$iz'd Stop- cock; $o that the Gla$s being turn'd up- $ide-down, the wide Orifice (which in common Gla$s-Helmets is the onely one) was upwards; and to that wide Orifice was fitted a ca$t-Cover of Lead, which was carefully cemented on to the Gla$s: Then the other Shank of the Stop-cock being with Cement likewi$e fa$ten'd into the upper part of the Pump, the ex$ucti- on of the Air was endeavoured. But it was not long before, the remaining Air being made much too weak to ballance the pre$$ure of the ambient Air, the Gla$s was not without a great noi$e crack'd al- mo$t half round, along that part of it where it began to bend inwards: As if in the Figure the crack had been made ac- cording to the Line <I>(ab);</I> and upon an <pb n=65> endeavour to pump out more of the Air, the crack once began, appear'd to run on further; though the Gla$s where it was broken $eem'd to be by conjecture above ten, $ome thought above twenty times as thick as the bubble mention'd in the fore- going Experiment. <p>This will perhaps make it $eem $trange, that having taken another Gla$s bubble blown at the $ame time, and like for ought we di$cern'd for $ize, thickne$s and Figure to that thin one formerly mention'd; and having $eal'd it up Her- metically, and $u$pended it in the Recei- ver, the ex$uction of the ambient Air did not enable the impri$oned Air to break, or in the lea$t to crack the bubble; though the Experiment were laboriou$ly try'd, and that $everal times with bubbles of o- ther $izes: But that perhaps the heat of the Candle or Lamp wherewith $uch Gla$$es are Hermetically $eal'd, (not to mention the warmth of his hands that $eal'd it) might $o rarifie the contained Air, as much to weaken its Spring, may $eem probable by the following Expe- riments. <pb n=66> <p>WE took a Gla$s Viol able to hold <MARG><I>Experi- ment</I> 9.</MARG> three or four Ounces of Water, and of the thickne$s u$ual in Gla$$es of that $ize; into the Neck of this was put a moderately $lender Pipe of Gla$s, which was carefully fa$ten'd with a mixture of e- qual parts of Pitch and Ro$in to the Neck of the Viol, and which reach'd almo$t to the bottom of it, as the $ixth Figure de- clares. <p>This Viol being upon a particular de- $ign fill'd with Water, till that came up in it a pretty deal higher then the lower end of the Pipe, was put into one of our $mall Receivers, (containing between a Pint and a Quart) in $uch manner as that the Gla$s Pipe, pa$$ing through a hole made purpo$ely for it in the Leaden-Cover of the Receiver, was for the mo$t part of it without the Ve$$el, which being exactly clo$ed, the Pump was $et awork: But at the very fir$t ex$uction, and before the Sucker was drawn to the bottom of the Cylinder, there flew out of the Viol a piece of Gla$s half as broad as the Palm of a Mans Hand, and it was thrown out with $uch violence, that hitting again$t <pb n=67> the Neighboring $ide of the Receiver, it not onely dafh'd it $elf to pieces, but crack'd the very Receiver in many places, with a great noi$e that much $urpri$ed all that were in the Room. But it $eem'd that in $o little a Receiver, the Air about the Viol being $uddenly drawn out, the Air Impri$on'd in the Ve$$el, having on it the whole pre$$ure of the Atmo$phere (to which by the Pipe open at both ends, It and the Water were expo$'d) and not having on the other $ide the wonted pre$- $ure of the Ambient Air to ballance that other pre$$ure, the re$i$tance of the Gla$s was finally $urmounted, and the Viol once beginning to break where it was weake$t, the external Air might ru$h in with vio- lence enough to throw the crack'd parcel $o forcibly again$t the Neighboring $ide of the Receiver, as to break that too. <p>And this may be pre$umed $ufficient to verifie what we delivered in that part of our Appendix to the fir$t Experiment, where we mention'd the almo$t equal pre$$ure of the Air on either $ide of a thin Gla$s Ve$$el, as the cau$e of its not being broken by the forcible Spring of the contain'd Air. But yet that it be not $u$pected that chance had an intere$t in $o <pb n=68> odde an Experiment as we have been Re- lating, we will adde that for farther $ati$- faction we reiterated it in a round Gla$$e containing by gue$$e about $ix ounces of water: this violl we put into $uch a $mall Receiver as was lately mention'd, in $uch manner as that the bottome of it re$ted upon the lower part of the Pneu- maticall Gla$$e, and the Neck came out through the Leaden-Cover of the $ame at a hole made purpo$ely for it. But be- ing made circum$pect by the foregoing mi$chance, we had put the violl into a Bladder, before we put it into the Re- ceiver to hinder this la$t named Gla$$e from being endanger'd by the breaking of the other. Then the Pneumaticall ve$$ell being clos'd $o that no way was left for the outward Air to get into it, but by breaking through the Viol, into who$e cavity it had free acce$$e by the mouth of it, (which was purpo$ely left open,) the Sucker being nimbly drawn down, the external Air immediatly pre$$'d forcibly as well upon the Leaden-Co- ver as the Violl; and the Cover hap- pening to be in one place a little narrow- er then the edge of the Pneumatical Gla$s, was depre$$'d, and thru$t into it $o vio- <pb n=69> lently by the incumbent Air, that get- ting a little within the tapering Lip of the Gla$s, it did like a kinde of Wedge, thru$t out that $ide where it was depre$$'d, $o as, though the Receiver was new, to $plit it. This accident being thus mention'd upon the by to confirm what we formerly $aid touching the fitne$s or unfitne$s of Gla$$es of $ome Figures to re$i$t the pre$$ure of the Atmo$phere; We will proceed to relate the remaining part of the Experi- ment, namely, That having fitted on a wider Cover to the $ame Receiver, and clo$ed both that and the crack with Ce- ment, we pro$ecuted the Experiment in the manner above related, with this $uc- ce$s: That upon the quick depre$$ing of the Sucker, the external Air bur$t the Body of the Viol in above a hundred pie- ces, many of them exceeding $mall, and that with $uch violence that we found a wide rent, be$ides many holes, made in the Bladder it $elf. <p>And to evince that the$e <I>Phænomena</I> were the effects of a limited and even moderate force, and not of $uch an ab- horrency of a <I>Vacuum</I> as that to avoid it, many have been plea$ed to think that Na- ture mu$t, upon occa$ion, exerci$e an al- <pb n=70> mo$t boundle$s power; we afterwards pur- po$ely try'd this Experiment with $everal Gla$$es $omewhat thicker then tho$e Vi- ols, and found the event to verifie our con- jecture, that it would not $ucceed: for the Gla$$es were taken out as intire as they were put in. <p>And here, My Lord, I hold it not un- fit, upon occa$ion of the mention that has been made of our having employ'd $mall Receivers, and one of them, not- with$tanding its being crack'd, to annex the$e two Adverti$ements. <p>Fir$t then, be$ides the great Pneuma- tical Gla$s $o often mention'd, and the proportionate Stop-cock, we thought fit to provide our $elves of $ome $mall Recei- vers blown of Cry$talline Gla$s, of $eve- rall Shapes, and furni$hed with $maller Stop-cocks purpo$ely made; and this we did upon hopes that when we had $ur- mounted the difficulties to be met with in Cementing the Gla$$es to the Stop- cocks, and the Pneumatical Ve$$els to the Pump $o exqui$itely as is requi$ite for our purpo$e, we $hould from the $malne$s of our Receivers receive a four-fold Advan- tage. The fir$t, that by rea$on of the $lenderne$s of the Ve$$els, and their be- <pb n=71> ing made of much purer and clearer me- tall, as the Gla$s-men $peak, then the great Receiver, we might have a more perfect view of every thing happening within them. The next, that $uch $mall Ve$$els might be empty'd with le$s la- bour and in much le$$e time. The third, that this nimble ex$uction of the ambient Air would make many changes in the Bodies $hut up in the$e gla$$es more $ud- den and con$picuous then otherwi$e they would prove. And the la$t, that we $hould be able to draw and keep out the Air much more perfectly from $uch $mall Ve$$els then from our large Receiver. But though we were not much di$-appointed in the expectation of the three fir$t advantages, yet we were in our hopes of the fourth. For be$ides the great difficulty we found in fitting together the Gla$$es, the Stop- cocks and the Covers; be$ides this I $ay, we found our $elves $eldom able to draw, and keep out the Air $o far as to make the remaining Air in the$e Receivers weaker then the remaining Air in our great Recei- ver. For though $ometimes the Leaks of $ome of the$e little Receivers may be much either fewer or $maller then tho$e of the larger Ve$$el; yet a little Air get- <pb n=72> ting into one of the$e, wherein it had but little room to expand and di$play it $elf, might pre$s as much upon all parts of the internal $urface of the Ve$$el, and upon the included Bodies, as a greater quan- tity of Air in a Ve$$el in who$e capacity it might finde more room to expand it $elf. <p>The other thing that we were to ad- verti$e, is, That 'tis not every $mall crack that can make $uch a Receiver as is of a roundi$h Figure altogether u$ele$s to our Experiment, in regard that upon the ex- $uction of the internal Air, the ambient Air on all $ides pre$$ing the Gla$s inwards or towards the middle, does con$equent- ly thru$t the Lips of the crack clo$er, and $o rather clo$e then increa$e it. <p>This I mention partly becau$e Recei- vers fit for our turn are more ea$ily crack'd then procur'd, and therefore ought not to be unnece$$arily thrown away as un$erviceable: And partly becau$e I think it becomes one that profe$$es him$elf a faithful Relator of Experiments, not to conceal from Your Lord$hip, that after a few of the foregoing Experiments were made, there happen'd in the great Recei- ver a crack of about a Span long, begin- <pb n=73> ning at the upper Orifice, and occa$ion'd, as it $eem'd, by the exce$$ive heat of too large an Iron that was employ'd to melt the Cement about that Orifice. But ha- ving laid upon this crack a broad Plai$ter, which in one of our E$$ays written $ome years $ince to your ingenious and hopeful Cou$in <I>Fones,</I> we extoll for the mending of crack'd Receivers, and other Chymi- cal Gla$$es; and having afterwards thick- ly over-laid this Plai$ter with Diachylon, we neither could then, nor can yet per- ceive that the Ve$$el leaks $en$ibly at that crack. <p>The Plai$ter was made of good quick Lime finely poudred, and nimbly ground with a Pe$tle in a Morter, with a quantity (I know not how much preci$ely, not ha- ving tho$e E$$ays in this place) of $cra- pings of Chee$e and a little fair Water, no more then is ju$t nece$$ary to bring the mixture to a $omewhat $oft Pa$te, which when the Ingredients are exqui$itely in- corporated, will have a $trong and $tincking $mell: Then it mu$t be im- mediately $pread upon a Linnen Cloath three or four fingers breadth, and pre$ently apply'd, le$t it begin to harden. But if Your Lord$hip had $een how we mended <pb n=74> with it Receivers even for the mo$t $ub- tle Chymical Spirits, You would $carce wonder at the $ervice it has done in our Pneumatical Gla$s. <p>WE took a Tallow-Candle of $uch <MARG><I>Experi- ment</I> 10.</MARG> a $ize that eight of them make about a pound, and having in a very com- modious Candle$tick let it down into the Receiver, and $o $u$pended it that the Flame burnt almo$t in the middle of the Ve$$el, we did in $ome two minutes ex- actly clo$e it up: and, upon Pumping ve- ry nimbly, we found that within little more then half a minute after the Flame went out, though the Snuff had been purpo$ely left of that length we judged the mo$t convenient for the la$ting of the Flame. <p>But the $econd time having put in the $ame Candle into the Receiver, (after it had by the bla$ts of a pair of Bellows been freed from Fumes) the Flame la$ted about two minutes from the time the Pumper began to draw out the Air; up- on the fir$t ex$uction whereof, the Flame $eem'd to contract it $elf in all its Dimen- $ions. And the$e things were further ob- <pb n=75> $ervable, that after the two or three fir$t ex$uctions of the Air, the Flame (except at the very top) appear'd exceeding blew, and that the Flame $till receded more and more from the Tallow, till at length it appear'd to po$$e$s onely the very top of the Week, and there it went out. <p>The $ame Candle being lighted again was $hut into the Receiver, to try how it would la$t there without drawing forth the Air, and we found that it la$ted much longer then formerly; and before it went out receded from the Tallow towards the the top of the Week, but not near $o much as in the former Experiment. <p>And having an intention to ob$erve par- ticularly what the motion of the $moak would be in the$e Experiments: We took notice that when the Air was not drawn out, there did upon the extinction of the Flame a con$iderable part of the Week remain kindled, which (probably by rea$on of the Circulation of the Air in the Ve$$el, occa$ion'd by the heat) e- mitted a Steam, which a$cended $wiftly and directly upwards in a $lender and unin- terrupted Cylinder of $moke, till it came to the top, whence it manife$tly recoyl'd by the $ides to the lower part of the Ve$- <pb n=76> $el. Whereas when the Flame went out upon the ex$uction of the Air one time (when the Flame retir'd very lea$urely to the top) we perceived it not to be fol- low'd by any $moke at all. And at an other time the upper part of the Week remaining kindled after the extinction of the Flame, the $lender $team of Fumes that did ari$e a$cended but a very little way, and then after $ome uncertain mo- tions this and that way, did, for the mo$t part, $oon fall downwards. <p>Being de$irous al$o to try whether there would be any difference as well in our Receiver as there is wont to be el$e- where betwixt Candles made of Wax and tho$e made of Tallow, as to their dura- tion; we took $lender Tapers of white Wax, (commonly called Virgins Wax) that being found to burn with much le$s $moke then common yellow Wax: Six of the$e of like bigne$s, and each of them of about the thickne$s of a Swans Quill, we pre$$'d together into one Candle: And having lighted all the Weeks, we let in the above-mention'd Wax into the Re- ceiver, and made what ha$te we could to clo$e it up with Cement. But though in the mean while we left open the Valve <pb n=77> of the Cylinder, the hole of the Stop- cock and that in the Cover of the Re- ceiver, that $ome Air might get in to cheri$h the Flame and the $moke might have a vent; Yet for $o great a Flame the Air $ufficed not $o much as till the Cover could be perfectly luted on: So that before we were quite ready to imploy the Pump, the Candle was extingui$hed. Wherefore we took but one of the a- bove mention'd Tapers, and having lighted it, clo$'d it up in the Receiver, to try how long a $mall Flame with a pro- portionable $moke would continue in $uch a quantity of Air: But we found upon two $everal tryals, that from the beginning of pumping, the Flame went out in about a minute of an hour. It appear'd indeed to us that the $winging of the Wier to and fro (in the Engine $haken by pumping) ha$ten'd the vani$h- ing of the Flame, which $eem'd by that motion to be ca$t $ometimes on one $ide of the Week and $ometimes on the o- ther; But though once we purpo$ely refrain'd pumping after a very few ex- $uctions of the Air, that the Flame might not be agitated, yet it la$ted not much longer then the newly mention'd time. <pb n=78> And la$tly, clo$ing up the $ame Taper, lighted again, to di$cover how long it would la$t without drawing out of the Air, we found that it burn'd for a while vividly enough, but afterwards began to be le$$en'd more and more in all its Di- men$ions. And we ob$erv'd that the Flame did not, as before, retire it $elf by little and little towards the top, but to- wards the bottom of the Week (from which yet it did a little withdraw upwards ju$t before it went out) $o that the upper part of the Week appear'd for a pretty while manife$tly above the top of the Flame, which having la$ted about five minutes, was $ucceeded by a directly a$- cending $tream of Smoak. <p>THere was taken a Wier, which being <MARG><I>Experi- ment</I> 11.</MARG> bent almo$t in the form of a Screw, con$tituted $uch an In$trument to contein Coals and leave them every way acce$$i- ble to the Air, as the tenth Figure de- clares; the breadth of this Ve$$el was no le$s then that it might with ea$e be con- vey'd into the Receiver: And having filld it to the height of about five Inches with throughly kindled Wood-coals, we let <pb n=79> it down into the Gla$s; and $peedily clo- $ing it, we cau$'d the Pumper to ply his work, and ob$erv'd that upon the ve- ry fir$t ex$uction of the Air (though per- haps not becau$e of that onely) the Fire in the Coals began to grow very dim, and though the agitation of the Ve$$el did make them $wing up and down (which in the free Air would have retarded the ex- tinction of the Fire) yet when we could no longer di$cern any redne$s at all in any of them; ca$ting our eyes upon a Minute- Watch we kept by us on this occa$ion, we found that from the beginning of the Pumping (which might be about two mi- nutes after the Coals had been put in glowing) to the total di$-appearing of the Fire, there had pa$$ed but three mi- nutes. <p>Whereupon, to try the Experiment a little further, we pre$ently took out the Coals, in which it $eems there had re- mained $ome little parcels of Fire, rather cover'd then totally quench'd: For in the open Air the Coals began to be re-kind- led in $everal places, wherefore having by $winging them about in the Wier, throughly lighted them the $econd time, welet them down again into the Receiver, <pb n=80> and clo$'d it $peedily as before; and then waiting till the Fire $eem'd totally ex- tinct without medling with the Pump, we found that from the time the Ve$$el was clo$'d till that no Fire at all could be per- ceiv'd there had pa$$ed about four mi- nutes: Whereby it $eem'd to appear that the drawing away of the ambient Air made the Fire go out $ooner then other- wi$e it would have done; though that part of the Air that we drew out left the more room for the $tifling $teams of the Coals to be received into. <p>La$tly, Having taken out the Wier and put other Coals into it, we did, in the $ame Room where the Engine $tood, let it hang quietly by a $tring in the open Air, to try how long the Fire would la$t with- out agitation when no Air was kept from it. And we found that the Fire began to go out fir$t at the top and out-$ides of the Coals; but inwards and near the bottom the Fire continu'd vi$ible for above half an hour, a great part of the Coals, e$pe- cially tho$e next the bottom, being burnt to a$hes before the Fire went out. <p>We cau$'d likewi$e a piece of Iron to be forg'd, of the bigne$s of a middle $iz'd Char-coal, and having made it red hot <pb n=81> throughout; we cau$'d it in the lately mention'd Wier, to be $peedily convey'd and $hut up into the Receiver, being de- $irous to try what would become of a glowing Body, by rea$on of its texture more vehemently hot then a burning Coal of the $ame bigne$s, & yet unlike to $end forth $uch copious & $tifling Fumes: But we could not ob$erve any manife$t change upon the ex$uction of the Air. The Iron began indeed to lo$e its Fiery redne$s at the top, but that $eem'd to be becau$e it was it the upper end $omewhat more $lender then at the lower: The red- ne$s, though it were in the day time, con- tinued vi$ible about four minutes; and then, before it did quite di$-appear, we turn'd the Key of the Stop-cock but could not di$cern any change of the Iron upon the ru$hing in of the Air. Yet $ome little remainders of Wax that $tuck to the Wier, and were turn'd into Fumes by the heat of the neighboring Iron, $eem'd to afford a more plentiful, or at lea$t a much more free expanded $moke when the Air was $uck'd out, then afterwards; though allowance was made for the de- crea$ing heat of the Iron. And la$tly, notwith$tanding a con$iderable ex$uction <pb n=82> of the ambient Air, though not by far $o great a one as might have been made by the Engine; and notwith$tanding the in- con$iderable di$$ipation of the parts of the Iron, the $urrounding $ides of the Recei- ver were $en$ibly, and almo$t offen$ively heated by it; in$omuch that a pretty while after the Iron was taken out, the $ides of the Gla$s manife$tly retain'd a warmth: which would not be unfit to be con$ider'd by a Per$on at more lea$ure then I am now. <p>BEing willing to try after this $ome- <MARG><I>Experi- ment</I> 12.</MARG> thing that would not cheri$h much Fire at once, and would keep Fire much longer then a Coal. We took a piece of Match, $uch as Souldiers u$e, of the thick- ne$s of a Mans little Finger, or $omewhat thicker; and this being well lighted at one end, was by a $tring $u$pended with that end downwards in the cavity of the Receiver which was immediately clo$'d: And yet by that time it could well be $o, the copious Fumes of the Match had neer fill'd and darken'd the Receiver. Where- fore, le$t the Ve$$el $hould be endanger'd, the Pump was nimbly ply'd, and a great <pb n=83> deal of Air and Smoke mixt together was drawn out, whereby the Receiver grow- ing more clear, we could di$cern the Fire in the Match to burn more and more lan- guidly: And notwith$tanding that by the diligence u$'d in Pumping, it $eem'd to have room enough allow'd it to throw out Fumes; yet after no long time it cea$'d from being di$cernable either by its Light or its Smoke. And though by that we were invited to $uppo$e it quite extingui$hed, yet we continu'd pumping a while, in pro$ecution of another Expe- riment we were trying at the $ame time: And this we did the more willingly be- cau$e of a $u$picion the Experiment a- bout the Coals might ea$ily $ugge$t, and which the event declar'd not to have been altogether groundle$s. For upon the Admi$$ion of the external Air, the Fire, that $eem'd to have gone out a pretty while before, did pre$ently revive; and being as it were refre$h d by the new Air, and blown by the Wind made by that Air in ru$hing in, it began again to $hine and di$$ipate the neighboring Fuel into Smoke as formerly. <pb n=84> <p>A While after we let down into <MARG><I>Experi- ment</I> 13.</MARG> the Receiver together with a ligh- ted piece of Match, a great Bladder well tyed at the Neck, but very lank, as not containing actually much (if any thing) a- bove a Pint of Air, but being capable of containing ten or twelve times as much. <p>Our $cope in this Experiment was partly to try whether or no the $moke of the Match, repleni$hing the Receiver, would be able to hinder the Dilatation of the inward Air, upon the ex$uction of the Ambient. And partly to di$cover whe- ther the extinction of the Fire in the Match did proceed from want of Air, or barely from the pre$$ure of its own Fumes, which for want of room to ex- pand them$elves in, might be $uppo$'d to Recoyl upon the Fire, and $o to $tifle it. <p>The event of our tryal was, That at the beginning of our Pumping the Match appear'd well lighted, though it had almo$t fill'd the Receiver with its plentiful Fumes: But by degrees it burnt more and more dimly, notwith- $tanding that by the nimble drawing <pb n=85> out the Air and Smoke, the Ve$$el were made le$s opacous, and le$s full of compre$$ing matter; as appeard by this, That the longer we pump'd, the le$$er Air and Smoke came out of the Cylin- der at the opening the Valve, and con$e- quently the le$s came into it before; yet the Fire in the Match went but $lowly out. And when afterwards, to $atisfie our $elves of its expiration, we had dar- ken'd the Room, and in vain endeavored to di$cover any $park of Fire, as we could not for $ome time before by the help of Candles di$cern the lea$t ri$ing of Smoke, we yet continued pumping $ix or $even times; and after all that letting in the Air, the $eemingly dead Fire quickly revived, and manife$ted its recovery by Light and $tore of Smoke, with the latter of which it quickly began to re- pleni$h the Receiver. Then we fell to pumping afre$h, and continued that labour $o long till the re-kindled Match went out again: and thinking it then fit not to cea$e from Pum- ping $o $oon as before, we found that in le$s then half a quarter of an hour the Fire was got out for good and all, <pb n=86> and pa$t the po$$ibility of being recover'd by the re-admitted Air. <p>Some Circum$tances, be$ides tho$e al- ready mention'd, occurr'd in the making of the Experiment, of which the$e are the principal. <p>Fir$t, when the Receiver was full of Smoke, if the Cylinder were emptied, immediately upon the turning of the Stop-cock, the Receiver would appear manife$tly darken'd to his eye that look'd upon the light through it: and this dark- ne$s was much le$s when the Receiver was much le$s fill'd with Fumes: It was al$o in$tantaneous, and $eem'd to proceed from a $udden change of place and $cituation in the exhalations, upon the vent $ud- denly afforded them and the Air they were mixt with, out of the Receiver into the Cylinder. <p>The next thing we ob$erv'd was, a kinde of <I>Halo</I> that appear'd a good while about the Fire, and $eem'd to be produced by the $urrounding Exhalations. <p>And la$tly, it is remarkable, That even when the Fumes $eemed mo$t to reple- ni$h the Receiver, they did not $en$ibly hinder the Air included in the Bladder from dilating it $elf after the $ame manner <pb n=87> (for ought we could di$cern) as it would have otherwi$e done: So that before the Fire or the Match was quite extinct, the Bladder appear'd $well'd at lea$t to $ix or $even times its former capacity. <p>Since the writing of the$e la$t Lines, we took a $mall Receiver, capable of containing (by gue$s) about a pound and a half of Water; and in the mid$t of it we $u$pended a lighted Match, but though within one minute of an hour (or there- abouts) from the putting in of the Match, we had cemented on the Cover, yet we could not make $uch ha$te, but that before we began to pump, the Smoke had $o fill'd that $mall Receiver, as for ought we di$cern'd, to choke the Fire. And having again and again reiterated the Experi- ment, it $eem'd $till as at fir$t, that we could not clo$e up the Ve$$el and pump out all the Fumes time enough to re$cue the Fire from Extinction; whereupon we made u$e of this Expedient. A$$oon as we had pump'd once or twice, we $udden- ly turn'd the Key, and thereby gave acce$s to the excluded Air, which ru$hing vio- lently in, as if it had been forced thorow a pair of Bellows, did both drive away the a$hes, fill the Gla$s with fre$h Air, and <pb n=88> by blowing the almo$t extingui$h'd Fire, re-kindl'd it, as appear'd by the Matches beginning again to $moke, which before it had cea$'d to do; we having by this means obtain'd a lighted Match in the Receiver, without being reduc'd to $pend time to clo$e it up, commanded the Air to be immediatly pump'd out, and found that upon the ex$uction of it, the Match quickly left $mokeing, as it $eem'd, by rea$on of the ab$ence of the Air; and yet if $ome urgent occa$ions had not hin- der'd us, we would for greater $ecurity have try'd, whether or no the Match re- kindled as formerly, would $moke much longer, in ca$e of no ex$uction of the am- bient Air. <p>TO try diver$e things at once, <MARG><I>Experi- ment</I> 14.</MARG> and particularly whether Fire, though we found it would not long la$t, might not yet be produced in our eva- cuated Receiver: We took a Pi$tol of about a Foot in length, and having firmly tyed it to a $tick almo$t as long as the Cavity of the Receiver, we very carefully prim'd it with well dry'd Gun- powder, and then cocking it, we ty'd to <pb n=89> the Tricker one end of a $tring, who$e other end was fa$ten'd to the Key former- ly mention'd to belong to the Cover of our Receiver. This done, we convey'd the Pi$tol, together with the annexed Staff, into the Ve$$el: which being clo$'d up, and empty'd after the u$ual man- ner, we began to turn the Key in the Cover; and thereby $hortning the $tring that reach'd from it to the Pi$tol, we pull'd a$ide the Tricker, and ob$erv'd, that according to our expectation the force of the Spring of the Lock was not $en$ibly abated by the ab$ence of the Air. (from who$e <I>impetus</I> yet $ome Modern Naturali$ts would derive the cau$e of the motion of Re$titution in $olid Bodies) For the Cock falling with its wonted violence upon the Steel, $truck out of it as many and as con$pi- cuous parts of Fire, as, for ought we could perceive, it would have done in the open Air. Repeating this Experi- ment divers times, we al$o ob$erved whether or no there would appear any con$iderable Diver$ity in the Motion of the $hining Sparks in a place where the remaining Aire was $o much rarified, but could not perceive <pb n=100> but that they moved $ome of them up- wards, as well as $ome of them down- wards, and $ome of them $ide-ways, as they are wont to do, when upon $uch col- li$ions they fly out in the open Air. <p>We likewi$e cau$'d a piece of Steel to be made of the form and bigne$s of the Flint, in who$e place we put it, and then the Pi$tol being cock'd and conveyed in- to the Receiver, the Trigger was pull'd after the Air was drawn out: And though the place were purpo$ely $omewhat dar- ken'd, yet there appear'd not upon the $triking of the two Steels again$t each o- ther the lea$t $park of Fire: Nor did we expect any (having before in vain attem- pted to $trike Fire this way in the open Air) though we thought fit to make the Experiment to undeceive tho$e who fan- cy in rarified Air, I know not what $trange di$po$ition, to take Fire upon a much $lighter occa$ion then this Experiment afforded. We have indeed found, that by the dextrous Colli$ion of two har- den'd pieces of Steel, $tore of $parks may be $truck out: But that was done with $uch vehement percu$$ion of the edges of the two Steels, as could not well be com- pa$$'d in our Receiver. <pb n=101> <p>But the chief thing we de$ign'd to do with our Pi$tol, was, To ob$erve whe- ther Gun-powder would take Fire in our empty'd and clo$ely $top'd Gla$s? Whe- ther the expan$ion of the Flame would be con$iderably varied by the ab$ence of $o much of the ambient Air as was drawn out of the Receiver? and whether the Flame would diffu$e it $elf upward, as it is wont, notwith$tanding its not having a- bout it the u$ual proportion of Air to force it up? And though mo$t of our at- tempts to fire the Gun-powder in the Pan of the Pi$tol $ucceeded not, becau$e we were fain to let it hang almo$t perpen- dicular in the Receiver; whereby the Powder was $haken down before the $parks could reach it: yet once the Ex- periment $ucceeded, and the kindled Powder $eem'd to make a more expanded Flame then it would have done in the open Air, but mounted upwards accord- ing to its wont, whether by rea$on of that little portion of Air, which in $pight of our pumping remained in the Receiver, or for any other cau$e, we have not now the lei$ure to con$ider. But we mu$t not for- get, that upon the extinction of the Flame the Receiver appear'd darken'd with <pb n=102> $moke, which $eem'd to move freely up and down, and upon the letting in the Air at the Stop-cock began to circulate much fa$ter then before. We wonld have made more ob$ervations concerning this Flame, but that of two or three attempts we afterwards made to repeat the kindling of Powder, not any one $ucceeded; and we have not the lea$ure to dwell long up- on one kinde of Tryals. <p>TO the$e Experiments concerning Fire <MARG><I>Experi- ment</I> 15.</MARG> we added another, which, though it $uc- ceded not, may perhaps without imper- tinency be recorded: partly becau$e that (as we have in another Treati$e amply de- clar'd) it is u$efull to recite what Experi- ments mi$carry as well as what $ucceed. And partly al$o becau$e it is very po$$ible that what we endeavored in vaine, may be performed by Your Lord$hip, or $ome other <I>Virtuo$o</I> that $hall have $lancker Ve$$ells then we had, and more Sunny dayes then the pre$ent Winter allows us. <p>We convey'd then into one of our $mall Receivers a piece of matter combu$tible, dry and black (experience declaring things <pb n=103> of that colour to be mo$t ea$ily kindled) & carefully clo$ing the Ve$$el we brought it to a Window at which the Sun, not very faire from the Meridian, $hone in very free- ly: then drawing out the Aire with $peed united the Sun-beames with a burning Gla$s upon the combu$tible matter which began immediatly to $end forth a Smoke that quickly darkned the Receiver, but notwith$tanding all our care and diligence the externall Aire got in $o fa$t that after diver$e tryals we were fayne to leave off the Experiment in that Gla$$e and induc'd to make tryall of it in our great Re- ceiver. <p>Haveing then after $ome difficulty lodg'd the combu$tible matter in the ca- vity of this Ve$$ell in $uch manner as that it was almo$t contiguous to that $ide thereof that was next the Sun, we did en- deavor with a pretty large burning Gla$s to kindle it, but found, as we fear'd, That by rea$on of the thickne$s of the Gla$s, (which was al$o of a le$s pure and le$s Diaphanous matter then the o- ther) the Sun-beams thrown in by the burning Gla$s, were in their pa$$age $o Di$located and Scattered (not now to mention tho$e many that being reflected, <pb n=104> I could not pierce into the cavity of the Receiver) that we could not po$$ibly u- nite enough of them to kindle the matter, nor $o much as to make it $en$ibly $moke. Yet we hope that the $eeing whether Bo- dies (other then Gun-powder) may be kindled, and what would happen to them when $et on fire, in a place in great mea- $ure devoid of Air, may prove $o Lucife- rous an Experiment, that when the Sea- $on is more favorable we $hall, God per- mitting, make further tryal of it, and ac- quaint Your Lord$hip with the Event, if it prove pro$perous. In the mean time we $hall pa$s on to other Experiments, a$$oon as we have adverti$'d Your Lord- $hip that we have forborn to make $uch Reflections upon the $everal Experiments we have $et down concerning Fire, as the matter would have ea$ily enough afford- ed, and Your Lord$hip may perhaps have expected. But I made the le$s $cruple to forbear the annexing of Speculations to the$e Recitals, becau$e <I>Carneades</I> & <I>Eleu- therius</I> have in $ome Dialogues concern- ing Heat and Flame, which were la$t year $een by $ome Friends, and may be, when you plea$e, commanded by You, men- <pb n=105> tion'd divers of my Thoughts and Expe- riments concerning Fire. <p>WE de$igned to try whether or no <MARG><I>Experi- ment</I> 16</MARG> divers Magnetical Experiments would exhibit any unu$ual <I>Phænomena,</I> being made in our Evacuated Receiver in$tead of the open Air: But for want of lei$ure and conveniency to pro$ecute $uch Tryals, we were induced to re$erve the re$t for an other time, and to content our $elves with making that which follows. We convey'd into the Receiver a little Pede$tal of Wood, in the mid$t of which was perpendicularly erected a $lender Iron, upon who$e $harp point an excited Needle of Steel purpo$ely made, and of about five Inches long, was $o placed that hanging in an <I>Æquilibrium</I> it could move freely towards either hand. Then the Air being after the u$ual manner pumped out, we apply'd a Load-$tone moderately vigorous to the out-$ide of of the Gla$s, and found that it Attracted or Repell'd the ends of the Needle, accor- ding to the Laws Magnetical, without any remarkable difference from what the $ame Load-$tone would have done had <pb n=106> none of the Air been drawn away from a- bout the Needle, which when the Load- $tone was removed, after $ome tremu- lous Vibrations to and fro, re$ted in a po- $ition wherein it look'd North and South. <p>PRoceed we now to the mention of <MARG><I>Experi- ment</I> 17.</MARG> that Experiment, whereof the $ati$- factory tryal was the principal Fruit I promi$'d my $elf from our Engine. It being then $ufficiently known, that, in the Experiment <I>De Vacuo,</I> the Quick- $ilver in the Tube is wont to remain ele- vated, above the $urface of that whereon it leans, about 27 digits: I con$idered, that, if the true and onely rea$on why the Quick-$ilver falls no lower, be, that at that Altitude, the Mercurial Cylinder in the Tube, is an <I>Æquilibrium</I> with the Cylinder of Air, $uppo$'d to reach from the adjacent Mercury to the top of the Atmo$phere: If this Experiment could be try'd out of the Atmo$phere, the Quick-$ilver in the Tube would fall down to a levell with that in the Ve$$el, $ince then there would be no pre$$ure up- on the Subjacent, to re$i$t the weight of <pb n=107> the Incumbent Mercury. Whence I in- ferr'd (as ea$ily I might) that, if the Ex- periment could be try'd in our Engine, the Quick-$ilver would $ub$ide below 27 Di- gits, in proportion to the ex$uction of Air, that $hould be made out of the Re- ceiver. For, as when the Air is $hut in- to the Receiver, it does (according to what hath above been taught) continue there as $trongly compre$$'d, as it did whil'$t all the incumbent Cylinder of the Atmo$phere lean'd immediatly upon it; becau$e the Gla$s, wherein it is pent up, hinders it to deliver it $elf, by an expan$i- on of its parts, from the pre$$ure where- with it was $hut up. So, if we could per- fectly draw the Air out of the Receiver, it would conduce as well to our purpo$e, as if we were allow'd to try the Experi- ment beyond the Atmo$phere. <p>Wherefore (after having $urmounted $ome little difficulties which occurr'd at the beginning) the Experiment was made after this manner. We took a $lender and very curiou$ly blown Cylinder of Gla$s, of near three Foot in length, and who$e bore had in Diameter a quarter of an Inch, wanting a hairs breadth: This Pipe being Hermetically $eal'd at one end, was, at <pb n=108> the other, fill'd with Quick-$ilver, care being taken in the filling, that as few bubles as was po$$ible $hould be left in the Mercury: Then the Tube being $topt with the Finger and inverted, was open'd, according to the manner of the Experi- ment, into a $omewhat long and $lender Cylindrical Box (in$tead of which we now are wont to u$e a Gla$s of the $ame form) half fill'd with Quick-$ilver: And $o, the liquid metal being $uffered to $ub$ide, and a piece of Paper being pa$ted on levell with its upper $urface, the Box and Tube and all were by $trings carefully let down into the Receiver, and then, by means of the hole formerly mention'd to be left in the Cover, the $aid Cover was $lip't along as much of the Tube as reach'd above the top of the Receiver; And the Interval, left betwixt the $ides of the Hole and tho$e of the Tube, was very exqui$itely fill'd up with melted (but not over hot) Diachylon; and the round chink, betwixt the Cover and the Receiver, was likewi$e very carefully clo$'d up: Upon which clo- $ure there appear'd not any change in the height of the Mercurial Cylinder; no more, then if the interpo$'d Gla$s Recei- ver did not hinder the immediate pre$$ure <pb n=109> of the ambient Atmo$phere upon the inclo$ed Air; which hereby appears to bear up on the Mercury, rather by virtue of its $pring, then of its weight: $ince its weight cannot be $uppo$'d to amount to above two or three Ounces, which is in- con$iderable in compari$on of $uch a Cy- linder of Mercury as it would keep from $ub$iding. <p>All things being thus in a readine$s, the Sucker was drawn down; and, immedi- ately upon the egre$s of a Cylinder of Air out of the Receiver; the Quick-$ilver in the Tube did, according to expectati- on, $ub$ide: and notice being carefully taken (by a mark fa$ten'd to the out$ide) of the place where it $topt, we cau$'d him that manag'd the Pump to pump again, and mark'd how low the Quick-$ilver fell at the $econd ex$uction; but continuing this work, we were quickly hindred from accurately marking the Stages made by the Mercury in its de$cent, becau$e it $oon $unk below the top of the Receiver; $o that we could thenceforward mark it no other ways then by the eye. And thus, continuing the labor of pumping for a- bout a quarter of an hour, we found our $elves unable to bring the Quick-$ilver in <pb n=110> the Tube totally to $ub$ide; becau$e, when the Receiver was con$iderably em- pty'd of its Air, and con$equently that little that remain'd grown unable to re$i$t the Irruption of the external, that Air would (in $pight of whatever we could do) pre$s in at $ome little Avenue or other; and though much could not there- at get in, yet a little was $ufficient to coun- terballance the pre$$ure of $o $mall a Cy- linder of Quick-$ilver, as then remain'd in the Tube. <p>Now (to $atisfie our $elves further, that the failing of the Quick-$ilver in the Tube to a determinate height, proceeds from the <I>Æquilibrium,</I> wherein it is at that height with the external Air, the one gravitating, the other pre$$ing with equal force upon the $ubjacent Mercury) we Re- turned the Key and let in $ome new Air; upon which the Mercury immediatly be- gan to a$cend (or rather to be impell'd up- wards) in the Tube, and continu'd a$cend- ing, till having Return'd the Key it im- mediatly re$ted at the height which it had then attain'd: And $o, by Turning and Returning the Key, we did $everal times at plea$ure impel it upwards, and check its a$cent. And la$tly, having given a free <pb n=111> egre$s at the Stop-cock to as much of the external Air as would come in, the Quick- $ilver was impell'd up almo$t to its fir$t height: I $ay almo$t, becau$e it $topt near a quarter of an Inch beneath the Pa- per mark formerly mention'd; which we a$crib'd to this, That there was (as is u- $ual in this Experiment) $ome little Parti- cles of Air engag'd among tho$e of the Quick-$ilver; which Particles, upon the de$cent of the Quick-$ilver, did manife$t- ly ri$e up in Bubbles towards the top of the Tube, and by their pre$$ure, as well as by le$$ening the Cylinder by as much room as they formerly took up in it, hin- der'd the Quick-$ilver from regaining its fir$t height. <p>This Experiment was a few days after repeated in the pre$ence of tho$e excellent and de$ervedly Famous Mathematick Profe$$ors, Dr. <I>Wallis,</I> Dr. <I>Ward,</I> and Mr. <I>Wren,</I> who were plea$ed to Honor it with their Pre$ence: And whom I name, both as ju$tly counting it an Honor to be known to them, and as being glad of $uch Judicious and illu$trious Witne$$es of our Experiment; and 'twas by their gue$s that the top of the Quick-$ilver in the Tube was defin'd to be brought within an Inch <pb n=112> of the $urface of that in the Ve$$el. <p>And here, for the Illu$tration of the foregoing Experiment, it will not be a- mi$s to mention $ome other particulars relating to it. <p>Fir$t then, When we endeavor'd to make the Experiment with the Tube clo$'d at one end with <I>Diachylon</I> in$tead of an Hermetical Seal; we perceiv'd, that upon the drawing of $ome of the Air out of the Receiver, the Mercury did indeed begin to fall, but continu'd afterwards to $ub$ide, though we did not continue pum- ping. Whence it appear'd, that though the <I>Diachylon</I> that $topt the end of the Tube were $o thick and $trong, that the external Air could not pre$s it in (as expe- rience taught us that it would have done, if there had been but little of it) yet the $ubt'ler parts of it were able (though $lowly) to in$inuate them$elves through the very body of the Plai$ter, which it $eems was of $o clo$e a Texture, as that which we mention'd our $elves to have $ucce$sfully made u$e of in the Experi- ment <I>De Vacuo</I> $ome years ago. So that now we begin to $u$pect, that perhaps one Rea$on, why we cannot perfectly pump out the Air, may be, that when the Ve$$el <pb n=113> is almo$t empty, $ome of the $ubtler parts of the external Air may, by the pre$$ure of the Atmo$phere, be $train'd through the very body of the <I>Diachylon</I> into the Receiver. But this is onely con- jecture: <p>Another Circum$tance of our Expe- riment was this, That, if (when the Quick-$ilver in the Tube was fallen low) too much ingre$s were, at the hole of the Stop-cock, $uddenly permitted to the ex- ternal Air; it would ru$h in with that vio- lence, and bear $o forcibly upon the $ur- face of the $ubjacent Quick-$ilver, that it would impel it up into the Tube rudely enough to endanger the breaking of the Gla$s. <p>We formerly mention'd, that the Quick-$ilver did not in its de$cent fall as much at a time after the two or three fir$t ex$uctions of the Air, as at the beginning: For, having mark'd its $everal Stages up- on the Tube, we found, that at the fir$t $uck it de$cended an Inch and 3/8, and at the $econd an Inch and 1/8; and when the Ve$- $el was almo$t empty'd, it would $carce at one ex$uction be drawn down above the breadth of a Barly-corn. And indeed we found it very difficult to mea$ure in what <pb n=114> proportion the$e decrements of the Mer- curial Cylinder did proceed: partly be- cau$e (as we have already intimated) the Quick $ilver was $oon drawn below the top of the Receiver: and partly becau$e, upon its de$cent at each ex$uction, it would immediatly rea$cend a little up- wards; either by rea$on of the leaking of the Ve$$el at $ome imperceptible hole or other, or by rea$on of the motion of Re$titution in the Air, which, b<*>ng $ome- what compre$t by the fall as well as weight of the Quick $ilver, would repell it a lit- tle upwards, and make it vibrate a little up and down, before they could reduce each other to $uch an <I>Æquilibrium</I> as both might re$t in. But though we could not hitherto make ob$ervations accurate e- nough concerning the mea$ures of the Quick-$ilver's de$cent, to reduce them in- to any <I>Hypothe$is,</I> yet would we not di$- courage any from attempting it: $ince, if it could be reduc'd to a certainty, tis proba- ble that the di$covery would not be un- u$eful. <p>And, to illu$trate this matter a little more, we will adde, That we made a $hift to try the Experiment in one of our above mention'd $mall Receivers, not containing <pb n=115> a Quart; but that (agreeably to what we formerly ob$erved) we found it as difficult to bring this to be quite empty as to eva- cuate the greater; the lea$t external Air that could get in (and we could not po$$i- bly keep it all perfectly out) $ufficing in $o $mall a Ve$$el to di$play a con$iderable pre$$ure upon the $urface of the Mercury, and thereby hinder that in the Tube from falling to a level with it. But this is remark- able, that having two or three times try'd the Experiment in that $mall Ve$$el, upon the very fir$t Cylinder of Air that was drawn out of the Receiver, the Mercury fell in the Tube 18 Inches and a half, and at another 19 Inches and a half. <p>But, on this occa$ion, I hold it not un- fit to give Your Lord$hip notice that I hop'd, from the de$cent of the Quick- $ilver in the Tube upon the fir$t $uck, to derive this advantage: that I $hould thence be enabled to give a near gue$s at the pro- portion of force betwixt the pre$$ure of the Air (according to its various $tates, as to Den$ity and Rarefaction) and the gra- vity of Quick-$ilver, then hitherto has been done. For in our Experiment there are diver$e things given, that may be made u$e of towards $uch a di$covery. <pb n=116> For fir$t we may know the capacity of the Receiver wherein the Experiment is made, $ince, by filling it with water, we may ea$ily compute how many Quarts, or Mea$ures of any other denomination, it contains of Air; which Air, when $hut up in the Ve$$el, may be $uppo$'d to have a pre$$ure equal to that of the Atmo- $phere; $ince it is able to keep the Quick- $ilver in the Tube from falling any lower then it did in the free and open Air. Next here is given us the capacity of the bra$s Cylinder empty'd by the drawing down of the Sucker (its bore and height being mention'd in the de$cription of our Pump) whereby we may come to know how much of the Air contain'd in the Recei- ver is drawn out at the fir$t $uck. And we may al$o ea$ily define, either in weight or cubick mea$ures the Cylinder of Quick-$ilver that an$wers to the Cy- linder of Air lately mention'd (that Mercuriall Cylinder being in our En- gine computable by deducting from the entire altitude or that Cylinder of Quick-$ilver, the altitude at which it re$ts upon the fir$t ex$uction.) But though, if this Experiment were very watchfully try'd in Ve$$els of $everal $izes, and the <pb n=117> various de$cents of the Quick-$ilver com- par'd among them$elves, 'tis not impro- bable that $ome $uch thing as we hop'd for may thereby be di$cover'd. Yet becau$e not onely the $olid contents of as much of the Gla$s-tube as remains within the concave $urface of the Receiver, and (which is more difficult) the varying con- tents of the Ve$$el containing the Mer- cury, and of as much of the Mercury it $elf as is not in the Tube, mu$t be dedu- cted out of the capacity of the Receiver; but there mu$t al$o an allowance be made for this, that the Cylinder that is empty'd by the drawing down of the Sucker, and comes to be fill'd upon the letting of the Air out of the Receiver into it, is not $o repleni$h'd with Air as the Receiver it $elf at fir$t was: becau$e there pa$$es no more Air out of the Receiver into the Cylin- der, then is requi$ite to reduce the Air in the cavity of the Cylinder, and in that of the Receiver to the $ame mea$ure of dila- tation: Becau$e of the$e (I $ay) and $ome other difficulties that require more skill in Mathematicks then I pretend to, and much more lea$ure then my pre$ent occa$ions would allow me, I was willing to refer the nicer con$ideration of this matter to $ome <pb n=118> of our Learned and Acurate Mathema- ticians, thinking it enough for me to have given the Hint already $ugge$ted. <p>For further confirmation of what hath been delivered, we likewi$e tryed the Ex- periment in a Tube of le$s then two foot long: and, when there was $o much Air drawn out of the Ve$$el, that the remain- ing Air was not able to counterballance the Mercurial Cylinder, the Quick-$ilver in the Tube $ub$ided $o vi$ibly, that (the Experiment being try'd in the little Ve$- $el lately mention'd) at the fir$t $uck it fell above a $pan, and was afterwards drawn lower and lower for a little while; and the external Air being let in upon it, impell'd it up again almo$t to the top of the Tube: So little matters it how heavy or light the Cylinder of Quick $ilver to $ub$ide is, provided its gravity over- power the pre$$ure of as much external Air as bears upon the $urface of that Mer- cury into which it is to fall. <p>La$tly we al$o ob$erv'd, That if (when the Mercury in the Tube had been drawn down, and by an Ingre$s permitted to the external Air, impell'd up again to its for- mer height) there were $ome more Air thru$t up by the help of the Pump into <pb n=119> the Receiver, the Quick-$ilver in the Tube would a$cend much above the wonted height of 27 digits, and immediatly up- on the letting out of that Air would fall a- gain to the height it re$ted at before. <p>Your Lord$hip will here perhaps expect, that as tho$e who have treated of the <I>Tor- ricellian</I> Experiment, have for the mo$t part maintaind the Affirmative, or the Ne- gative of that famous Que$tion, Whether or no that Noble Experiment infer a <I>Va- cuum?</I> $o I $hould on this occa$ion inter- po$e my Opinion touching that Contro- ver$ie, or at lea$t declare whether or no, in our Engine, the ex$uction of the Air do prove the place de$erted by the Air $uck'd out, to be truly empty, that is, devoid of all Corporeal Sub$tance. But be$ides that, I have neither the lei$ure, nor the ability, to enter into a $olemn Debate of $o nice a Que$tion; Your Lord$hip may, if you think it worth the trouble, in the Dia- logues not long $ince referr'd to, finde the Difficulties on both $ides repre$ented; which then made me yield but a very wa- vering a$$ent to either of the parties con- tending about the Que$tion: Nor dare I yet take upon me to determine $o difficult a Controver$ie. <pb n=120> <p>For on the one $ide it appears, that not- with$tanding the ex$uction of the Air, our Receiver may not be de$titute of all Bo- dies, $ince any thing placed in it, may be $een there; which would not be, if it were not pervious to tho$e Beams of Light which rebounding from the $een Object to our eyes, affect us with the $en$e of it: And that either the$e Beams are Corporeal Emanations from $ome lucid body, or el$e at lea$t the light they convey doth re$ult from the brisk Motion of $ome $ubtle Matter, I could, if I mi$take not, $ufficiently manife$t out of the Dialogues above-mention'd, if I thought your Lord- $hip could $eriou$ly imagine that Light could be convey'd without, at lea$t, having (if I may $o $peak) a Body for its Ve- hicle. <p>By the $ixteenth Experiment, it al$o appears that the clo$ene$s of our Receiver hinders it not from admitting the Efflu- via of the Load-$tone; which makes it very probable that it al$o freely admits the Magnetical $teams of the Earth; con- cerning which, we have in another Trea- ti$e endeavour'd to manife$t that numbers of them do always permeate our Air. <p>But on the other $ide it may be $aid, <pb n=121> That as for the $ubtle Matter which makes the Objects enclo$ed in our evacuated Re- ceiver, vi$ible, and the Magnetical Efflu- via of the Earth that may be pre$um'd to pa$s thorow it, though we $hould grant our Ve$$el not to be quite devoyd of them, yet we cannot $o rea$onably affirm it to be repleni$h'd with them, as we may $uppo$e, that if they were gather'd toge- ther into one place without Intervals be- tween them, they would fill but a $mall part of the whole Receiver. As in the thirteenth Experiment, a piece of Match was incon$iderable for its bulk, while$t its parts lay clo$e together, that afterwards (when the Fire had $catter'd them into $moke) $eem'd to repleni$h all the Ve$$el. For (as el$ewhere our Experiments have demon$trated) both Light and the Efflu- via of the Load-$tone, may be readily ad- mitted into a Gla$s, Hermetically $eal'd, though before their Admi$$ion, as full of Air as hollow Bodies here below are wont to be, $o that upon the ex$uction of the Air, the large $pace de$erted by it, may remain empty, notwith$tanding the pre- tence of tho$e $ubtle Corpu$cles, by which Lucid and Magnetical Bodies pro- duce their effects. <pb n=122> <p>And as for the Allegations above mention'd, they $eem to prove but that the Receiver devoy'd of Air, <I>May</I> be re- pleni$h'd with $ome $uch Etherial Matter, as $ome Modern Naturali$ts write of; but not that it really <I>is</I> $o. And indeed to me it yet $eems, that as to tho$e $paces which the <I>Vacui$ts</I> would have to be empty, be- cau$e they are manife$tly devoid of Air; and all gro$$er Bodies, the <I>Pleni$ts</I> (if I may $o call them) do not prove that $uch $paces are repleni$h'd with $uch a $ubtle Matter as they $peak of, by any $en$ible effects, or operations of it (of which di- vers new Tryals purpo$ely made, have not yet $hown me any) but onely conclude that there mu$t be $uch a Body, becau$e there cannot be a Void. And the rea$on why there cannot be a Void, being by them taken, not from any Experiments, or <I>Phænomena</I> of Nature, that clearly and particularly prove their <I>Hypothe$is,</I> but from their notion of a Body, who$e Na- ture, according to them, con$i$ting one- ly in exten$ion (which indeed $eems the property mo$t e$$ential to, becau$e in$epa- rable from a Body) to $ay a $pace devoid of Body, is to $peak in the School-mens Phra$e, a Contradiction <I>in Adjecto:</I> This <pb n=123> rea$on, I $ay, being thus de$um'd, $eems to make the Controver$ie about a <I>Vacu- um,</I> rather a Metaphy$ical, then a Phy$io- logical Que$tion; which therefore we $hall here no longer debate, finding it very dif- ficult either to $atisfie Naturali$ts with this Carte$ian Notion of a Body, or to manife$t wherein it is erroneous, and $ub- $titute a better in its $tead. <p>But though we are unwilling to exa- mine any further the Inferences wont to be made from the <I>Torricellian</I> Experi- ment, yet we think it not impertinent to pre$ent Your Lord$hip with a couple of Adverti$ements concerning it. <p>Fir$t, then if in trying the Experiment here or el$ewhere, you make u$e of the Engli$h mea$ures that Mathematicians and Trade$men are here wont to imploy, You will, unle$s you be forewarn'd of it, be apt to $u$pect that tho$e that have writ- ten of the Experiment have been mi$ta- ken. For whereas men are wont gene- rally to talk of the Quick-$ilver's remain- ing $u$pended at the heighth of between $ix or $even and twenty Inches; we com- monly ob$erv'd, when divers years $ince we fir$t were $ollicitous about this Expe- riment, that the Quick-$ilver in the Tube <pb n=124> re$ted at about 29 Inches & an half above the $urface of the Re$tagnant Quick-$ilver in the Ve$$el, which did at fir$t both amaze and perplex us, becau$e though we held it not improbable that the difference of the gro$$er Engli$h Air, and that of <I>Italy</I> and <I>France,</I> might keep the Quick-$ilver from falling quite as low in this colder, as in tho$e warmer Climates; yet we could not believe that that difference in the Air $hould alone be able to make $o great a one in the heights of the Mercurial Cylinders; and accordingly upon enquiry we found, that though the various den$ity of the Air be not to be over-look'd in this Ex- periment, yet the main Rea$on why we found the Cylinder of Mercury to con$i$t of $o many Inches, was this, That our Engli$h Inches are $omewhat inferior in length to the digits made u$e of in Fo- rein Parts, by the Writers of the Expe- riment. <p>The next thing I de$ire Your Lord$hip to take notice of, is, That the heigth of the Mercurial Cylinder is not wont to be foũd altogether $o great as really it might prove, by rea$on of the negligence or in- cogitancy of mo$t that make the Experi- ment. For often times upon the opening <pb n=125> of the inverted Tube into the Ve$$ell'd Mercury, you may ob$erve a bubble of Air to a$cend from the bottom of the Tube through the $ub$iding Quick-$ilver to the top; and almo$t always you may, if you look narrowly, take notice of a multitude of $mall bubbles all along the in$ide of the Tube betwixt the Quick- $ilver & the gla$s: (not now to mention the Particles of Air that lye conceal'd in the very Body of the Mercury) Many of which, upon the Quick-$ilvers for$aking the upper part of the Tube, do break in- to that de$erted $pace where they finde little or no re$i$tance to their expanding of them$elves. Whether this be the rea- $on that upon the Application of warm Bodies to the emptyed part of the Tube, the $ubjacent Mercury would be depre$$'d $omewhat lower, we $hall not determine; though it $eem very probable, e$pecially $ince we found that upon the application of Linnen cloaths dipped in Water, to the $ame part of the Tube, the Quick- $ilver would $omewhat a$cend, as if the cold had conden$'d the Impri$on'd Air, that pre$$'d upon it, into a le$$er room. But that the de$erted $pace is not wont to be totally devoid of Air, we were induc'd <pb n=126> to think by $everal Circum$tances. For when an eminent Mathematician, and ex- cellent Experimenter, had taken great pains and $pent much time in accuratly fil- ling up a Tube of Mercury, we found that yet there remain'd $tore of incon$pi- cuous bubbles, by inverting the Tube, letting the Quick-$ilver fall to its wonted heighth; and by approaching (by de- grees) a red hot Iron to the out-$ide of the Tube, over again$t the upper part of the Mercurial Cylinder, for hereby the little unheeded bubbles, being mightily expan- ded, a$cended in $uch numbers, and $o fa$t to the de$erted $pace, that the upper part of the Quick-$ilver $eem'd, to our wonder, to boyl. We further ob$erv'd, That in the tryals of the <I>Torricellian</I> Experiment we have $een made by others, and (one excepted) all our own, we never found that upon the inclining of the Tube the Quick- $ilver would fully reach to the very top of the $eal'd end: which argued, that there was $ome Air retreated thither that kept the Mercury out of the unrepleni$h'd $pace. <p>If Your Lord$hip $hould now demand what are the be$t expedients to hinder the intru$ion of the Air in this Experiment; <pb n=127> we mu$t an$wer, That of tho$e which are ea$ily intelligible without ocular demon- $tration, we can at pre$ent $ugge$t upon our own tryals no better then the$e. Fir$t, at the open end of the Tube the Gla$s mu$t not onely be made as even at the ed- ges as you can, but it is very conveni- ent (e$pecially if the Tube be large) that the bottom be every way bent inwards, that $o the Orifice, not much exceeding a quarter of an Inch in Diameter, may be the more ea$ily and exactly $topp'd by the Experimenter's finger; between which and the Quick-$ilver, that there may be no Air intercepted (as very often it hap- pens that there is) it is requi$ite that the Tube be fill'd as full as po$$ibly it can be, that the finger which is to $top it, pre$$ing upon the accumulated and protuberant Mercury, may rather throw down $ome, then not finde enough exactly to keep out the Air. It is al$o an u$eful and compen- dious way not to fill the Tube at fir$t quite ful of Mercury, but to leave near the top about a qnarter of an Inch empty; for if you then $top the open end with your finger, and invert the Tube that quarter of an Inch of Air will a$cend in a great bubble to the top, and in its pa$$age thi- <pb n=128> ther, will gather up all the little bubbles, and unite them with it$elf into one great one, $o that if by reinverting the Tube you let that bubble return to the open end of it, you will have a much clo$er Mer- curial Cylinder then before, and need but to adde a very little Quick-$ilver more to fill up the Tube exactly. And la$tly, as for tho$e le$$er and incon$picuous parcels of Air which cannot this way be gleaned up, You may endeavor before you invert the Tube, to free the Quick-$ilver from them by $haking the Tube, and gently knock- ing on the out-$ide of it, after every little parcel of Quick-$ilver which you pour in; and afterwards, by forcing the $mall la- titant bubbles of Air to di$clo$e them- $elves and break, by imploying a hot Iron in $uch manner as we lately mention'd. I remember that by carefully filling the Tube, though yet it were not quite free from Air, we have made the Mercurial Cylinder reach to 30 Inches and above an eighth, and this in a very $hort Tube: which we therefore mention, becau$e we have found, by experience, that in $hort Tubes a little Air is more prejudicial to the Experiment then in long ones, where the Air having more room to expand it <pb n=129> $elf, does le$s potently pre$s upon the $ub- jacent Mercury. <p>And $ince we are fallen upon the con$i- deration of the Altitude of the Mercurial Cylinder, I mu$t not conceal from Your Lord$hip an Experiment relating thereun- to, which perhaps will $et both You and many of your Friends the <I>Virtuo$i</I> a think- ing; and, by di$clo$ing $ome things a- bout the Air or Atmo$phere that have $carce hitherto been taken notice of, may afford you $ome hints conducive to a fur- ther di$covery of the $ubject of this E- pi$tle. <p>WE took a Gla$s Tube, which, <MARG><I>Experi- ment</I> 18.</MARG> though it were not much above three Foot long, we made choice of be- cau$e it was of a more then ordinarily even thickne$s. This we fill'd with Mer- cury, though not with as much care as we could, yet with $omewhat more then is wont to be u$ed in making the <I>Torricellian</I> Experiment. Then, having according to the manner inverted the Tube, and open'd the mouth of it beneath the $urface of $ome other Quick-$ilver, that in the Tube fell down to the wonted heigth, leaving, <pb n=130> as is u$ual, $ome little Particles of Air in the $pace it de$erted, as we ghe$t by ob- $erving, that upon the Application of hot Bodies to the upper part of the Tube, the Quick-$ilver would be a little depre$$'d. La$tly, having put both the Tube and the Ve$$el it lean'd on into a convenient Wooden Frame, to keep them from mi$- chances: we plac'd that Frame in a Win- dow within my Bed-chamber, that I might both keep the Mercury from being $tirr'd, and have opportunity to watch from time to time the <I>Phænomena</I> it was to exhibit. For the better di$covery of which, when the Quick-$ilver both in the Tube and $ubjacent Ve$$el was perfectly at re$t, we took notice, by a mark made on the out- $ide of the Gla$s, how high the included Liquor then reach'd. <p>During $everal Weeks that the Tube was kept in that Window (which was very rarely open'd) I had the opportunity to ob$erve, that the Quick-$ilver did $ome- times faintly imitate the Liquor of a Weather-gla$s, $ub$iding a little in warm, and ri$ing a little in cold Weather, which we a$cribed to the greater or le$$er pre$$ure of that little Air that remain'd at the top of the Tube, expanded or conden$'d by <pb n=131> the heat or cold that affected the ambient Air. But that which I was chiefly careful to ob$erve, was this, That oftentimes the Quick-$ilver did ri$e and fall in the Tube, and that very notably, without conforming it $elf to what is u$ual in Weather-gla$$es, who$e Air is at the top, nay quite contrary thereunto: for $ometimes I ob$erv'd it in very cold weather ($uch as this Winter has already afforded us good $tore of) to fall down much lower then at other times, when by rea$on of the ab$ence of both Fro$t, Snow, and $harp Winds, the Air was comparatively much warmer. And I fur- ther ob$erv'd, That $ometimes the Quick- $ilver would for $ome days together re$t almo$t at the $ame height; and at other times again it would in the compa$s of the $ame day con$iderably vary its altitude, though there appear'd no change either in the Air abroad, or in the temper of the Air within the Room (wherein was con$tantly kept a good Fire) nor in any thing el$e, to which either I, or $ome eminently Learned Men whom I then acquainted with the Experiment, could rea$onably impute $uch a change: E$pecially con$idering that the $pace wherein the Mercury wandred up and down, within about five Weeks, a- mounted to full two Inches, of which we <pb n=132> found by our $everal marks whereby we had taken notice of its $everal removes, that it had de$c&etilde;ded about (9/16) of an Inch from the place where it fir$t $etled, & the other Inch and (7/16) it had a$cended. And it $eems pro- bable that the height of the Mercurial Cy- linder would have varied yet more, if the Experiment had been made in the open Air and in a long Tube, where the Parti- cles of the Impri$on'd Air, by having more room to di$play them$elves in, might not have had $o $trong a Spring to work upon the Quick-$ilver with. But for want both of time and of a competent quantity of Mercury (which was not to be procur'd where we then happen'd to be) we were unable to make any further try- als: which therefore chiefly troubled us, becau$e we would gladly have try'd an in- genious Experiment which was $ugge$ted unto us by that excellent Mathematician Mr. <I>Wren,</I> who being invited to name any thing he would have us try touching the pre$$ure of the Air, de$ired us to ob$erve whether or no the Quick-$ilver in a long Tube would not a little vary its height ac- cording to the Tides, e$pecially about the New and Full Moon, about which times Mariners ob$erve tho$e great Flowings and Ebbs of the Sea, that they call the <pb n=133> Spring-Tides. For he $agaciou$ly and plau$ibly conjectur'd that $uch ob$ervati- ons accurately made, would di$cover the truth or erroneou$ne$s of the <I>Carte$ian Hypothe$is</I> concerning the Ebbing and Flowing of the Sea: which <I>Des Cartes</I> a$cribes to the greater pre$$ure made upon the Air by the Moon, and the Intercur- rent Ethereal Sub$tance at certain times (of the Day, and of the Lunary Moneth) then at others. But in regard we found the Quick-$ilver in the Tube to move up and down $o uncertainly, by rea$on, as it $eems, of accidental mutation in the Air; I $omewhat doubt whether we $hall finde the Altitude of the Quick-$ilver to vary as regularly as the Experiment is ingeni- ou$ly propo$'d. The $ucce$s we $hall (God permitting us to make tryal of it) acquaint Your Lord$hip with; and in the mean time take notice, that when we had occa- $ion to take the Tube out of the Frame (after it had $taid there part of <I>November</I> and part of <I>December</I>) a good Fire being then in the room, becau$e it was a Snowy day, we found the Quick-$ilver in the Tube to be above the upper $urface of the $ubjacent Mercury 29 Inches three quarters. <pb n=134> <p>If Your Lord$hip $hould now ask me what are the true cau$es of this varying al- titude of the Mercurial Cylinder; I $hould not undertake to an$wer $o difficult a que- $tion, and $hould venter to $ay no more, then that among divers po$$ible cau$es to which it may be a$cribed, it would not be, perhaps, ab$urd to reckon the$e that fol- low. <p>Fir$t then we may con$ider, that the Air in the upper part of the Tube is much more rarified, and therefore more weak then the external Air, as may appear by this among other things, That upon the in- clining of the Tube the Quick-$ilver will readily a$cend almo$t to the very top of it, and $o take up eight or nine tenth parts, and perhaps more of that $pace which it de$erted before: which would not happen if that whole $pace had been full of unra- rified Air, $ince that (as tryal may ea$ily $atisfie you) would not have $uffer'd it $elf to be thru$t into $o narrow a room by $o weak a pre$$ure. So that although in our Tube when the included Air was heated, the Quick-$ilver was $omewhat depre$$'d: Yet there is this difference be- twixt $uch a Tube and common Weather- Gla$$es, that in the$e the included and the <pb n=135> ambient Air are in an <I>Æquilibrium</I> as to pre$$ure, and the weight of the Water that keeps them $eparate is $carce con$i- derable. Whereas in $uch a Tube as we are $peaking of, the Air within is very much more dilated then that without; and 'tis not $o much the $pring or re$i$tance of the included Air, as the weight of the Mercurial Cylinder it $elf that hinders the Quick-$ilver from a$cending higher; for if we $hould $uppo$e that de$erted part of the Tube perfectly devoid of Air, yet would the Quick-$ilver ri$e but a little higher in it, and be far from filling it, in regard the outward Air would not be able to impel up $uch a weight much higher: whereas it may, by our former Experiments appear, that if all the Air in the upper part of a Weather-Gla$s were away, the Water would be impell'd up to the very top of it, though the Pipe were above thirty Foot long. <p>We may next con$ider, that this ra- rified Air at the upper part of our Tube being exactly $hut up betwixt the Gla$s and the Quick-$ilver, it was $carce $ubject to any di$cernable alterations, $ave tho$e it receiv'd from heat and cold. <pb n=136> <p>And we may further con$ider that yet the external Air or Atmo$phere is $ubject to many alterations, be$ides them that proceed from either of tho$e Quali- ties. <p>For the Experiment that occa$ion'd this Di$cour$e, $eems to make it proba- ble enough that there may be $trange Ebbings and Flowings, as it were, in the Atmo$phere; or at lea$t, that it may ad- mit great and $udden Mutations, either as to its Altitude or its Den$ity, from cau$es, as well unknown to us, as the effects are unheeded by us. And that You may not think that there is nothing in Nature but our Experiment that agrees with this our conjecture, we might put Your Lord$hip in minde of the Pains and Aches that are often complain'd of by tho$e that have had great Wounds or Brui$es, and that doe pre$age great Mutations in the Air oftentimes, whil$t to $trong and healthy Per$ons no $ign of any $uch thing appears. And that is al$o very memorable to this purpo$e, which I remember I have $ome- where read in a Book of the Ingenious <I>Kircherus,</I> who giving a pertinent admoni- tion concerning the various refractions that may happen in the Air, relates, That <pb n=137> during his $tay in <I>Malta,</I> he often $aw Mount <I>Ætna,</I> though the next day, not- with$tanding its being extreamly clear, he could not $ee it; adding, that <I>Vintemillius,</I> a very Learned Per$on, did oftentimes, from a Hill he names, behold the whole I$land he calls <I>Luprica</I> protuberant above the Sea, though at other times, notwith- $tanding a clear Sky, he could not $ee it. And though perhaps this may be in part a- $cribed to the various light & po$ition of the $un, or to the various di$po$ition of the Spectators eye, or peradventure to $ome other cau$e; yet the mo$t probable cau$e $eems to be the differing Den$ity of the Air, occa$ion'd by Exhalations capable to increa$e the refraction, and con$equently bring Beams to the Eye, which otherwi$e would not fall on it. We have likewi$e in another Treati$e mention'd our having often ob$erv'd with Tele$copes a plenty of Steams in the Air, which without $uch a help would not be taken notice of, and which as they were not at all times to be $een even through a Tele$cope, $o they did $ometimes, e$pecially after a $hower of Rain, ha$tily di$appear: and when we have vi$ited tho$e places that abound with Mines, we have $everal times been told <pb n=138> by the Diggers, that even when the Sky $eem'd clear, there would not $eldom $ud- denly ari$e, and $ometimes long continue, a certain Steam (which they u$ually call a damp) $o gro$s and thick, that it would oftentimes put out their very Candles, if they did not $ea$onably prevent it. And I think it will ea$ily be granted, that the a$cen$ion of $uch Steams into this or that part of the Air, and their mixing with it, are very like to thicken it; as on the o- ther $ide either heat or the $udden conden- $ation of the Air in another part of the At- mo$phere (to mention now no other cau- $es) are capable of rarifying it. <p>Nor will it very much import the main $cope of our Di$cour$e, whether it be $uppo$'d that the copious Steams the earth $ends into the air, thicken that part of the Atmo$phere that receives them, and make it more heavy: Or that $ome- times the Fumes may a$cend with $uch ce- lerity, that though the Air be thicken'd yet they rather dimini$h then en<*>ea$e its gravitation, in regard that the quickne$s of their a$cent, not onely keeps them from gravitating them$elves, but may hinder the pre$$ing downwards of many Aërial Corpu$cles that they meet with in <pb n=139> their way upwards. This, I $ay, is of no great importance to our pre$ent Di$- cour$e, $ince either way the Terre$trial Steam may here and there con$iderably alter the gravity or pre$$ure of the At- mo$phere. <p>Your Lord$hip may al$o be plea$ed to remember, That by our $eventeenth Ex- periment it appear'd that as when the Air in the Receiver was expanded more then ordinarily, the Quick-$ilver in the Tube did proportionably $ub$ide; $o when the Air in the $ame Receiver was a little more then ordinarily compre$$'d, it did impell up the Quick-$ilver in the Tube above the wonted height of betwixt $ix and $e- ven and twenty digits. <p>And if to the$e things we annex, that for ought we can finde by tryals purpo$e- ly made, the degree of rarity or den$ity of the Air, $hut up into our Receiver, does not $en$ibly alter its temperature as to cold or heat. It will not, I hope, appear ab$urd to conceive, That $ince the Air, included in the Tube, could but very faint- ly hinder the a$cent of the Quick-$ilver, or pre$s it downwards, $ince too that inclu- ded Air could $carce immediately receive any $en$ible alteration, $ave either by heat <pb n=140> or cold. And $ince al$o that according to the bare den$ity or rarity of the Air in- cumbent on the $ubjacent Quick-$ilver in the Ve$$el, that in the Tube was impell'd more or le$s high; $uch changes happen- ing in the neighboring part of the out- ward Air, either by the a$cen$ion of gro$s or copious exhalations, or by any other cau$e (of which there may be divers) as were capable to make con$iderable altera- tions in the con$i$tence of the Air, as to rarity and den$ity, <I>may</I> be able propor- tionably to alter the heighth of the Quick-$ilver: I rather $ay, that $uch alte- rations <I>may</I> be, then that they <I>are</I> the cau$es of our <I>Phænomenon,</I> becau$e I think it $ufficient, if I have propo$'d conje- ctures not altogether irrational about a new My$tery of Nature, touching which, the chief thing I pretend to, is to give oc- ca$ion to the Curious to inquire further into it then I have been yet able to do. <p>THe $ame Rea$on that mov'd us to <MARG><I>Experi- ment</I> 19.</MARG> conclude, that by the drawing of the Air out of the Receiver, the Mercury would de$cend in a Tube $horter then $ix and twenty digits, induc'd us al$o to ex- <pb n=141> pect, that by the $ame means Water might be brought to $ub$ide in Gla$s Tubes of a moderate length, though by the noble Experiment, $aid to have been accurately made in <I>France</I> by <I>Mon$ieur Pa$chal,</I> we are informed that a Tube of no le$s then about two and thirty Foot, was found requi$ite to make the Experi- ment <I>De Vacuo</I> $ucceed with Water in- $tead of Quick-$ilver: $o tall a Cylinder of that lighter Liquor, being, it $eems, requi$ite to equal the weight of a Mercu- rial Cylinder of $ix or $even and twenty digits, and $urmount the pre$$ure of the Atmo$phere. <p>We took then a Tube of Gla$s, Her- metically $eal'd at one end, of about four foot in length, and not very $lender: This at the open end we fill'd with common Water, and then $topt that end till we had inverted the Tube, and open'd it be- neath the $urface of a quantity of the like Water, contain'd in a $omewhat deep and $lender Ve$$el. This Ve$$el, with the Tube in it, was let down into the Recei- ver, and the Receiver being clo$'d up af- ter the accu$tom'd manner, the Pump was $et awork. <pb n=142> <p>As much of the event as concerns our pre$ent purpo$e, was this, That till a con- $iderable part of the Air was drawn out of the Receiver, the Tube continu'd top- full of Water as when it was put in, it be- ing requi$ite that a great part of the Air formerly contain'd in the Receiver, $hould be drawn out, to bring the remaining Air to an <I>Æquilibrium</I> with $o $hort and light a Cylinder of Water. But when once the Water began to fall in the Tube, then each ex$uction of Air made it de- $cend a little lower, though nothing near $o much as the Quick-$ilver at the begin- ning did in the Experiment formerly men- tion'd. Nor did there appear $o much inequality in the $paces tran$mitted by the Water in its de$cent, as there did in tho$e ob$erv'd in the fall of the Quick- $ilver, of which the cau$e will $carce $eem ab$tru$e to him that $hall duly reflect up- on what has been already deliver'd. And whereas we drew down the Quick-$ilver in the Tube $o far as to bring it within an Inch of the $urface of the other Quick- $ilver into which it was to fall; the lowe$t we were able to draw down the Water was, by our conjecture, to about a Foot <pb n=143> or more above the $urface of that in the Ve$$el; of which I know not whether it will be needful to a$$ign $o obvious a cau$e as that, though the little Air remaining in the Receiver could not hinder a Cylin- der of above an Inch high of Quick-$ilver from $ub$iding; yet it might very well be able, by its pre$$ure, to countervail the weight of a Cylinder of a Foot long or more, of a Liquor $o much le$s ponderous then Quick-$ilver, as Water is. And in fine, to conclude our Experiment, when the Water was drawn down thus low, we found, that by letting in the outward Air, it might be immediately impell'd up a- gain to the higher parts of the Tube. <p>We will adde no more concerning this Experiment, $ave that having try'd it in one of our $mall Receivers, we ob$erv'd, That upon the fir$t ex$uction of the Air the Water did u$ually $ub$ide divers In- ches, and at the $econd (ex$uction) fall down much lower, $ub$iding $ometimes near two Foot; as al$o that upon the let- ting in of the Air from without, the Wa- ter was impell'd up with very great ce- lerity. <pb n=144> <p>THat the Air has a notable Ela$tical <MARG><I>Experi- ment</I> 20.</MARG> power (whence$oever that proceeds) we have, I $uppo$e, abundantly evinc'd, and it begins to be acknowledg'd by the eminente$t Modern Naturali$ts. But whe- ther or no there be in Water $o much as a languid one, $eems hitherto to have been $carce con$ider'd, nor has been yet, for ought I know, determin'd either way by any Writer, which invited us to make the following Experiment. <p>There was taken a great Gla$s-bubble, with a long neck; ($uch as Chymi$ts are wont to call a Philo$ophical Egg) which being fill'd with common Water till the Liquor reach'd about a $pan above the bubble, and a piece of Paper being there pa$ted on, was put un$top'd into the Re- ceiver, and then the Air was $uck'd out after the wonted manner. The event was this, That a con$iderable part of the Air, pent up in the Receiver, was drawn out before we di$cern'd any expan$ion of the Water; but, continuing the labor of pumping, the Water manife$tly began to a$cend in the $tem of the Gla$s, and di- vers bubbles loo$ening them$elves from <pb n=145> the lower parts of the Ve$$el, made their way through the Body of the Water, to the top of it, and there brake into the Receiver: And after the Water once ap- pear'd to $well, then at each time the Stop- cock was turn'd to let out the air from the Receiver into the Pump, the Water in the Neck of the Gla$s did $uddenly ri$e a- bout the breadth of a Barly-corn in the Neck of the Gla$s, and $o attain'd, by degrees, to a con$iderable height above the mark formerly mention'd. And at length (to make the expan$ion of the Wa- ter more evident) the outward Air was $uddenly let in, and the Water immedi- ately $ub$ided and de$erted all the $pace it had newly gain'd in the Gla$s. <p>And, on this occa$ion, it will not per- haps be ami$s to acquaint Your Lord$hip here (though we have already mention'd it in another Paper, to another purpo$e) with another Expedient that we made u$e of two or three years ago, to try whether or no Water had a Spring in it. About that time then, That Great and Learned Promoter of Experimental Philo$ophy Dr. <I>Wilkins,</I> doing me the Honor to come him$elf, and bring $ome of his in- qui$itive Friends to my Lodging, we <pb n=146> there had in readine$s a round and hollow Ve$$el of Pewter, great enough to con- tain two pounds of Water, and exactly clo$e every where, but at one little hole where it was to be fill'd; then partly by $ucking out the Air, and partly by inject- ing Water with a Syringe, it was (not without $ome difficulty) fill'd up to the top; and that hole being plac'd directly upwards, there was a little more Water lei$urely forc'd in by the Syringe. Upon which, though the Ve$$el were permitted to re$t, and the hole kept in its former po- $ture, yet the compre$$'d Water lei$urely $well'd above the Orifice of the hole, and divers drops ran over along the $ides of the Ve$$el. After this, we cau$'d a skilful Pew- terer (who had made the Globe) to clo$e it up in our pre$ence with Soder $o exqui- $itely, that none $u$pected there was any thing left in it be$ides Water. And la$t- ly, the Ve$$el thus $oder'd up, was wari- ly and often $truck in divers places with a Wooden Mallet, and thereby was mani- fe$tly compre$$ d, whereby the inclo$ed Water was crouded into le$s room then it had before: And thereupon when we took a Needle, and with it and the Mallet per- forated the Ve$$el, and drew out the <pb n=147> Needle again; the Water (but in a very $lender Stream) was $uddenly thrown af- ter it into the Air, to the height of two or three Feet. As for the other <I>Phænome- na</I> of this Experiment, $ince they belong not to our pre$ent purpo$e, and are partly mention'd in another of our Papers, we $hall, in$tead of recording them here, give this Adverti$ement: That as evidently as this Experiment, and that made in our Receiver, $eem to prove a power in the Water to expand and re$tore it $elf after compre$$ion; yet for a rea$on to be met with ere long, I judged it not $afe to in- fer that Conclu$ion from the$e Premi$es, till I had made $ome of the following try- als, to the mention of which I will there- fore ha$ten. <p>TO di$cover whether the Expan$ion <MARG><I>Experi- ment</I> 21.</MARG> of the Water really proceeded from an Ela$tical power in the parts of the Water it $elf, we thought it requi$ite to try two things: The one, Whether or no the Atmo$phere gravitates upon Bodies under Water; and the other, Whether in ca$e it do gravitate, the Intume$cence of the Water may not be a$cribed to $ome <pb n=148> $ub$tance $ubtler then it $elf, re$iding m- it. In order to the $atisfying my $elf about the fir$t of the$e, I intended to let down into the Receiver a Ve$$el of Water, wherein $hould be immer$'d a very $mall oyl'd Bladder, almo$t devoid of Air, but $trongly <*>'d up at the Neck with a $tring, and detain'd a little under Water by $uch a weight fa$ten'd to that $tring, as $hould ju$t be able to keep the Bladder from $wimming, and no more. For I $uppo$'d, that if when all things were thus order'd, the Receiver were empty'd, in ca$e there were any $uch pre$$ure of the Atmo$phere upon Water, as I was inclin'd to believe, the Air within the Bladder, being upon the ex$uction of the Air within the Receiver, freed from that pre$$ure, and being pre$$'d onely by the $mall weight of the in- cumbent Water, would con$iderably ex- pand it $elf; but whil'$t we were prepa- ring Bladders for this Experiment, there occurr'd an ea$ie way for the making at once both the Di$coveries I de$ir'd. <p>We took then a Gla$s Viol, containing by ghe$s a pound and $ome ounces of Water, this we fill'd top full, and then we put into the Neck of it a Gla$s Pipe a pretty deal bigger then a Goo$e Quill, <pb n=149> open at both ends, and of divers Inches in length: One end of this Pipe was $o put into the Neck of the Viol, as to reach a little below it, and then was carefully cemented thereto that no Air might get into the Viol, nor no Water get out of it, otherwi$e then through the Pipe; and then the Pipe being warily fill'd, about half way up to the top, with more Wa- ter, and a mark being pa$ted over again$t the upper $urface of the Liquor; the Viol thus fitted with the Pipe, was, by $trings let down into the Receiver, and according to the wonted manner exqui$itely clo$'d up in it. <p>This done, we began to Pump out the Air, and when a pretty quantity of it had been drawn away, the Water in the Pipe began to ri$e higher in the Pipe, at the $ides of which $ome little bubbles di$co- ver'd them$elves. After a little while longer, the Water $till $welling, there appear'd at the bottom of the Pipe a bub- ble about the bigne$s of a $mall Pea, which a$cending through the Pipe to the top of the Water, $taid there awhile and then broke; but the Pump being nimbly ply'd, the expan$ion of the Water $o en- crea$'d, that quickly, getting up to the <pb n=150> top of the Pipe $ome drops of it be- gan to run down along the out-$ide of it, which oblig'd us to forbear pumping a- while, and give the Water leave to $ub- $ide within le$s then two Inches of the bottom of the Pipe. After this the Pump being again $et at work, the bub- bles began to a$cend from the bottom of the Pipe, being not all of a $ize, but yet $o big, that e$timating one with another, they appear'd to be of the $ize of the $mal- ler $ort of Peas; and of the$e we reckon'd about $ixty which came up one after ano- ther, be$ides $tore of $maller ones, of which we made no reckoning: And at length, growing weary of reckoning and pumping too (becau$e we found, that in $pight of all our pains and indu$try, $ome un- di$cern'd Leak or other in the Recei- ver hinder'd us from being able to empty it altogether) we thought fit to de$i$t for that time. After tryal made of what o- peration the external Air, being let in upon the expanded Water, would have; and accordingly turning the Key to let in the Air, we $aw, as we expected, that the Water in the Pipe in a moment fell down almo$t to the bottom of it. <pb n=151> <p>Now of this Experiment there are two or three Circum$tances yet to be men- tion'd, which are no le$s then tho$e alrea- dy recited, pertinent to our pre$ent pur- po$e. <p>In the fir$t place then, when the great- er part of the Air had been pump'd out of the Receiver, the ri$ing bubbles a$cend- ed $o very $lowly in the Pipe, that their Progre$s was $carce di$cernable; which $eem'd to proceed from this, That their bigne$s was $uch, That they could not $ufficiently extend them$elves in the cavity of the Gla$s, without pre$$ing on both hands again$t the $ides of it, whereby they became of more difficult extru$ion to the Water. And though it may $eem $trange the$e bubbles $hould be of any con$iderable bulk, $ince 'tis like they con$i$ted of le$$er parcels of the Air lurking in the Water, then tho$e that were vigorous enough to make their way through long before them: yet they were commonly much larger then before, $ome of them being equal in quantity to four or five Peas: Whether this their in- crea$e of bulk proceeded from the greater decrement of the pre$$ure of the Air, <pb n=152> or from the Union of two or three of tho$e numerous bubbles which were then generated below the bottom of the Pipe, where we could not $ee what was done a- mong them. <p>Another thing we noted in our bubbles was, That whereas in ordinary ones the Air, together with the thin film of Water that inve$ts and detains, is wont to $well above the $urface of the Water it $wims on, and commonly to con$titute Hemi$- pherical Bodies with it, the little parcels of Air that came up after the Receiver was pretty well empty'd, did not make protuberant bubbles, but $uch who$e up- per $urface was either level with or be- neath that of the Water, $o that the up- per $urface being u$ually $omewhat con- vex, the le$s protuberant parts of it had a pretty quantity of Water remaining a- bove them. <p>We al$o further ob$erv'd, That where- as in the bubbles that fir$t appear'd in the Pipe, the a$cending Air did, as in o- ther common bubbles, make its way up- wards, by dividing the Water through which it pa$$'d, in tho$e bubbles that ap- pear'd at the latter end of our Experi- ment, when the pre$$ure of the little ex- <pb n=153> ternal Air, remaining in the Receiver, was grown incon$iderable, the a$cending parcels of Air having now little more then the weight of the incumbent Water to $urmount, were able both $o to expand them$elves as to fill up that part of the Pipe which they pervaded, & by pre$$ing every way again$t the $ides of it, to lift upwards with them what Water they found above them, without letting any con$iderable quantity glide down along the $ides of the Gla$s: So that $ometimes we could $ee a bubble thru$t on before it a whole Cylinder of Water of perhaps an Inch high, and carry it up to the top of the Pipe; though as we formerly no- ted, upon the letting in the external Air, the$e tumid bubbles $uddenly relap$'d to their former incon$picuou$ne$s. <p>All the$e things laid together $eem'd $ufficiently to confirm that, which the con$ideration of the thing it $elf would ea$ily enough per$wade, namely, That the Air, and $uch like Bodies being under Water, may be pre$$'d upon as well by the Atmo$phere, as by the weight of the incumbent Water it $elf. <p>Hence likewi$e we may verifie what we ob$erv'd at the clo$e of the foregoing <pb n=154> Experiment, namely, That from the $ole $welling of Water there recorded, it can- not be $o $afely concluded that Water, when freed from compre$$ion, is endowd with an Ela$tical power of expanding it $elf, $ince thereby it appears that the In- tume$cence produc'd by that Experiment, may (at lea$t in great part) be a$crib'd to the numerous little bubbles which are wont to be produc'd in Water, from which the pre$$ure of the Atmo$phere is in great mea$ure taken off. So apt are we to be mi$-led, even by Experiments them- $elves, into Mi$takes, when either we con- $ider not that mo$t Effects may proceed from various Cau$es, or minde onely tho$e Circum$tances of our Experiment, which $eem to comply with our preconceiv'd <I>Hypothe$is</I> or Conjectures. <p>And hence it $eems al$o probable, that in the Pores or invi$ible little rece$$es of Water it $elf there lie commonly inter- $per$'d many parcels of either Air, or at lea$t $omething Analogous thereunto, al- though $o very $mall that they have not been hitherto $o much as $u$pected to lurk there. But if it be demanded how it appears that there is inter$per$'d through the Body of Water any $ub$tance thinner <pb n=155> then it $elf, and why that which produc'd the bubbles above mention'd $hould not be re$olutely $aid to be nothing el$e then a more active and $pirituous part of the Water, we $hall, in order to the Elucida- tion of this matter, $ubjoyn to what was formerly deliver'd the following Ex- periment. <p>WE recited in our nineteenth Ex- periment, how by drawing mo$t <MARG><I>Experi- ment</I> 22.</MARG> of the Air out of the Receiver, we made the Water $ub$ide by degrees in a Gla$s not four Foot long: We $hall now adde, that in the like Experiment made in $uch a Tube, or a greater, it may be ob$erv'd, That when the Water begins to fall, there will appear $tore of bubbles fa$ten'd all a- long to the $ides of the Gla$s; of which bubbles, by the agitation of the Ve$$el con$equent upon pumping, there will ari$e good numbers to the top of the Water, and there break; and as the Cylinder of Water is brought to be lower and lower, $o the bubbles will appear more numerous in that part of the Tube which the Water yet fills; and the nearer the $urface of the Water, in its de$cent, approaches to the$e <pb n=156> bubbles, the greater they will grow, be- cau$e having the le$s weight and pre$$ure upon them, the Expan$ion of that Air which makes them, can be the le$s re$i$ted by the pre$$ure of the incumbent Water and Air; as $eems probable from hence, that upon the letting in a little external Air, tho$e bubbles immediately $hrink. <p>It may indeed, as we lately intimated, be conjectur'd, that the$e bubbles pro- ceed not $o much from any Air pre-exi- $tent in the Water, and lurking in the Pores of it, as from the more $ubtle parts of the Water it $elf; which by the expan- $ion allow'd them upon the dimini$h'd pre$$ure of the ambient Bodies may gene- rate $uch bubbles. And indeed, I am not yet $o well $atisfied that bubbles may not (at lea$t $ometimes) have $uch an Origina- tion: but that which makes me $u$pect that tho$e in our tryals contain'd real Air formerly latitant in the Pores of the Wa- ter, is this, That upon the inletting of the external Air, the Water was not again impell'd to the very top of the Tube whence it began to fall, but was $topt in its a$cent near an Inch beneath the top. And $ince, if the upper part of the Tube had been devoyd of any other <pb n=157> then $uch Ethereal matter as was $ubtle enough freely to penetrate the pores of the Gla$s, the external Air would have been able to impel the Water to the top of a Tube $even or eight times as long as ours was; The <I>Phænomenon</I> under con$i- deration $eem'd manife$tly to argue that the many bubbles that broke at the top of the Water did contain a real Air, which, being collected into one place and hinder'd by the top of the Gla$s from re- ceding, was able to with$tand the pre$$ure of the outward Air. As we $ee that if never $o little Air remain in the Tube up- on the making the Experiment <I>De Vacuo</I> with Quick-$ilver, no inclining of the Tube, though a long one, will enable a Man to impel the Mercury up to the very top, by rea$on (as we formerly noted) of the re$i$tance of the included Air, which will not be compre$$'d beyond a certain degree. <p>But in order to a further Di$covery what our bubbles were, we will, on this occa- $ion, inform Your Lord$hip that we try'd the XIX<SUP>th</SUP> <I>Experiment</I> in one of our $mall Receivers, and $ound, that upon the draw- ing down of the Water, $o many bubbles di$clo$'d them$elves and broke into the <pb n=158> upper part of the Tube, that having after- wards let in the external Air, the Water was not thereby impell'd to the top of the Tube (three Foot in length) within a lit- tle more then half an Inch. And whe- ther or no it were Air that po$$e$$'d that $pace at the top of the Tube which was not fill'd with Water, we took this cour$e to examine. We drew the $econd time the Air out of the Receiver, and found, that by rea$on of the body that po$$e$$'d the top of the Tube, we were able not onely to make the Water in the Tube fall to a level with the $urface of the Water in the Ve$$el: But al$o (by plying the Pump a little longer) a great way beneath it: which $ince it could not well be a$crib'd to the bare $ub$iding of the Water by rea- $on of its own weight, argued that the Wa- ter was depre$$'d by the Air: which was confirm'd by the Figure of the $urface of the Water in the Tube, which was much more concave then that of Water in Tubes of that bigne$s u$es to be. And this further tryal (to adde that upon the by) we made at the $ame time, That when the Water in the Pipe was drawn down almo$t as low as the Water without it, we ob$erv'd, that (though we de$i$ted <pb n=159> from pumping) by the bare application of a hand moderately warm to the de$ert- ed part of the Tube, the remaining Wa- ter would be $peedily and notably de- pre$$'d. And having for a while held a kindled Coal to the out$ide of the Tube, (the Pump being $till unimploy'd, becau$e the Ve$$el chanced to hold extraordinarily well) the Air was by the heat $o far ex- panded, that it quickly drave the Water to the bottom of the Tube, which was divers Inches beneath the $urface of the ambient Water. Whereby it appears (by the $ame way by which we formerly mea- $ur'd the dilatation of the Air) that the Air, even when it is expanded to between 90 and 100 times, its extent will yet rea- dily admit of a much further rarifaction by heat. <p>I con$ider'd al$o that in ca$e the Bub- bles we have been $peaking of, were pro- duc'd by the parcels of Air latitant in the Water, that Air being now got together to the top of the Tube, though the Air were again drawn out of the Receiver, the taking off its pre$$ure would not di$- clo$e bubbles as before; and accordingly, the Air being again pump'd out, the Wa- ter in the Tube de$cended as formerly: <pb n=160> but for a great while we $carce $aw one bubble appear, onely when the Receiver had been very much exhau$ted, and the Water was fallen very low, there appear'd near the bottom of the Tube, certain little bubbles, which $eem'd to con$i$t of $uch parcels of Air as had not, by rea$on of their $malne$s, got up to the top of the Water, with the more bulkie and vi- gorous ones. And that which is not in- con$iderable, is, That having, by letting in the Air, forc'd up the Water into the Tube, we could not perceive that it a$- cended nearer the top, though we per- mitted the Engine to remain unimploy'd for two or three Nights together, and watch'd whether the Water would $well up and fill the Tube. And on this occa- $ion I remember, that having try'd $uch an Experiment as this with Quick-$ilver in- $tead of Water, in a Tube of about a Foot and a half long, wherein it might $eem more hopeful to e$cape bubbles; yet up- on the drawing down the Quick-$ilver as low as we could, and letting in the exter- nal Air upon it, we found that $ome lurk- ing particles of Air were got up to the top of the Tube, and hinder'd the Quick- $ilver from being forc'd up again $o high. <pb n=161> And though the Quick-$ilver were by this means brought to appear a very clo$e and lovely Metalline Cylinder, not inter- rupted by inter$per$'d bubbles as before; yet having cau$'d the Air to be again drawn out of the Receiver, I could per- ceive $everal little bubbles to di$clo$e them$elves, fa$ten'd to the in$ide of the Tube, near the bottom of it; and having purpo$ely watch'd one or two of the chief- e$t, I had the plea$ure to ob$erve, that though they grew bigger and bigger as the $urface of the Mercurial Cylinder fell nearer and nearer to them, $o as that at length they $well'd into a con$picuous bulk; yet upon the wary letting in the Air upon them, they did not break, but pre$ently $hrunk up into a littlene$s that render'd them incon$picuous. <p>Whence it $eems very probable, if not certain, that even in the clo$e$t and mo$t ponderous Liquors, and therefore much more in Water, there may lurk undi$cern- able parcels of Air, capable, upon the removal of the pre$$ure of the ambient Air (though but in part) and that of the Liquor wherein it lurks, to produce con- $picuous bubbles. And con$equently, if it $eem inconvenient to admit an Ela$tical <pb n=162> power in the Water, it may be $aid that the $welling of the compre$$'d Water in the Pewter Ve$$el lately mention'd, and the $pringing up of the Water at the hole made by the Needle, were not the effects of any internal <I>Elater</I> of the Water, but of the $pring of the many little particles of Air di$per$'d through that Water, and acting upon it in their $udden recovering them$elves to a greater extent, then that to which a violent compre$$ion had re- duc'd them. <p>But though, from all the$e particulars, it $eems manife$t that the bubbles we have been all this while treating of, were pro- duc'd by $uch a $ub$tance as may be pro- perly enough call'd Air; yet till we $hall have had the opportunity of making $ome further tryals concerning the nature of the Air, we $hall not re$olutely deter- mine whether or no Air be a Primogenial Body (if I may $o $peak) that cannot now be generated or turn'd either into Water or any other Body. Yet in the mean while (becau$e it is an important Que$tion, and if rightly determin'd, may much conduce to the knowledge of the <pb n=163> nature of the Air) We think it not unfit to make a brief mention of $ome of the particulars which at pre$ent occur to our thoughts in favor of either part of the Que$tion. <p>Fir$t then, divers Naturali$ts e$teem the Air (as well as other Elements) to be in- generable and incorruptible. And rea$ons plau$ible enough may be drawn to coun- tenance this Opinion from the con$idera- tion of that permanency that ought to belong to the corporeal Principles of o- ther Bodies. <p>Next, Experience may be pleaded to the $ame purpo$e, for I have read of $ome who have in vain attempted to turn Air into Water, or VVater into Air. <p>The diligent <I>Schottus</I> tells us, That a- <MARG><I>Schottus <*></I> Part 3. Cla$$. 1.</MARG> mong$t the other rarities to be met with in that great Repo$itory of them, the <I>Mu$æum Kercherianum,</I> there is a round Gla$s with a tapering Neck near half full (as one may gue$s by the Scheme he an- nexes) of ordinary Spring-water, which having been Hermetically $hut up there by <I>Clavius</I> the famous Geometrician, The included water is to this day pre- $erv'd, not onely clear and pure, as if it were but newly put in: But (as it $eems) <pb n=164> without (in the lea$t) turning into Air, notwith$tanding its having been kept there the$e fifty years: For he tells us, That the Water hath continued there all this while without any diminution. <p>Nor does it appear in tho$e Gla$$es, which for Chymical Experiments we u$u- ally clo$e with <I>Hermes</I> his Seal (as they call it) that the included Air does, during its long Impri$onment, notwith$tanding the alteration it receives from various de- grees of heat, di$cernably alter its nature. Whereas we plainly perceive in our Dige- $tions and Di$tillations, that though it may be rarified into invi$ible Vapors, yet it is not really chang'd into Air, but onely divided by heat, and $catter'd into very minute parts, which meeting together in the Alembick or in the Receiver, do pre- $ently return into $uch Water as they con- $tituted before. And we al$o $ee, that ev'n Spirit of Wine, and other $ubtle and fugitive Spirits, though they ea$ily fly in- to the Air, and mingle with it, do yet in the Gla$$es of Chymi$ts ea$ily lay a$ide the di$gui$e of Air, and re$ume the deve- $ted form of Liquors. And $o volatile Salts, as of Urine, Harts-horn, <I>&c.</I> though they will readily di$per$e them$elves <pb n=165> through the Air, and play up and down in the capacity of an Alembick or a Recei- ver: yet will they, after a while, fa$ten them$elves to the in$ides of $uch Gla$$es in the form of Salts. <p>Be$ides, $ince Air is confe$$edly en- dow'd with an Ela$tical power that proba- bly proceeds from its Texture, it appears not what it is that in $uch light alterations of Water, as are by many pre$um'd ca- pable of turning it into Air, can be rea- $onably $uppo$'d $o to contrive the Parti- cles of Water, as to give them, and that permanently, the $tructure requi$ite to a Spring. I adde the word, Permanently, becau$e the newly mention'd ob$ervations $eem to argue the Corpu$cles of Air to be irreducible into Water, whereas the Aqueous Particles may perhaps for a while be $o vehemently agitated, as to pre$s almo$t like Springs upon other Bo- dies; yet upon the cea$ing of the agitati- on, they quickly, by relap$ing into Wa- ter, di$clo$e them$elves to have been no- thing el$e whil'$t they counterfeited the Air. <p>La$tly, The Experiment formerly made in our Engine with a piece of Match, $eems to evince, that even tho$e light and <pb n=166> $ubtle Fumes (for the mo$t part not aque- ous neither) into which the Fire it $elf $hatters dry Bodies, have no $uch Spring in them as the Air, $ince they were unable to hinder or repre$s the expan$ion of the Air included in the Bladder they $urroun- ded. <p>I remember indeed that the Learned <MARG><I>Natural & <*> Hi$t. <*> In- <*>,</I> Lib. 3. <*> 9.</MARG> <I>Fo$ephus Aco$ta,</I> in his Hi$tory of the <I>We$t Indies,</I> tells us, That he $aw in tho$e parts $ome Grates of Iron $o ru$ted and con$um'd by the Air, that the Metal be- ing pre$$'d between the Fingers, di$$olv'd (to u$e his words) to powder, as if it had been Hay or parched Straw. And I re- <MARG><I>Geogr. Ge- <*>ral.</I> Lib. <*> 19.</MARG> member too, that the accurate <I>Varenius</I> tells us, That in the I$lands commonly called <I>Azores,</I> the Air (and Wind) is $o $harp, that in a $hort time it frets not only Iron Plates, but the very Tiles upon the Roofs of Hou$es, and reduces them to du$t. And I have el$ewhere mention'd $ome recent Ob$ervations of this kinde. But it may be $aid, That the above-men- tion'd Authors a$cribe the recited effects chiefly to the Winds, and that however the corro$ion of the Iron and the Tiles may proceed not from the Air it $elf, or any of its genuine parts, but from $ome <pb n=167> $aline Corpu$cles di$per$'d through the Air, and driven by the Winds again$t the Bodies it is pre$um'd to fret. And that $uch volatile Salts may copiou$ly a$cend into the Air, and yet retain their Nature, as doth the more fixt Salt in the Sea Wa- ter, the $ublimations of <I>Sal-Armoniack</I> may $ufficiently evince. Not to mention that I have $hown $ome Friends a $ecret kinde of $aline Sub$tance incomparably $ubtler then <I>Sal-Armoniack,</I> which did not onely ea$ily enough a$cend it $elf, but carried up with it (and that in a very great proportion) the $olid and ponderous Bo- dy ev'n of uncalcin'd Gold in the form of $ubtle exhalations, which did afterwards fa$ten them$elves to the upper parts of the Ve$$els, and yet manife$t them$elves to continue Gold. We remember al$o, that to try whether Water could be turn'd into Air, we once took an <I>Æolipile,</I> into which we had before convey'd $ome Wa- ter, and placing it upon kindled Coals when the heat forc'd out a vehement $tream of aqueous Vapors; we ty'd about the neck of it, that of a Bladder, which we had before empty'd of Air; and find- ing the <I>Æolipile</I> after a while to blow up the Bladder, we carefully ty'd it again <pb n=168> that the included $ub$tance might not get away. Then $lipping it off from the <I>Æo- lipile</I> we convey'd it into our Receiver, to try whether or no that which in part di- $tended the Bladder would appear by its Spring to be true Air: whereby we found that upon the ex$uction of the ambient Air, the included $ub$tance expanded it $elf and the Bladder to a very much great- er bulk then it was of before. And for further $atisfaction, having again taken out the Bladder, we $uffer'd it to remain ty'd up till next morning, to try whether time, and the coldne$s of the night, would make the contain'd $ub$tance relap$e in- to Water: But the next Morning we found it little le$s tumid then before. I remember, I $ay, that I once made this Experiment; but I might $ay in an$wer to it, that the chief rea$on of my men- tioning it, is, To let Your Lord$hip $ee how requi$ite it is to be circum$pect and con$iderate, when we are to make and to build upon nice Experiments. For though I may $eem to have u$ed $ufficient cauti- on, yet afterward con$idering with my $elf that the <I>Æolipile</I> I had imploy'd was a very large one, and that it required much more care then one that has not try'd it <pb n=169> would imagine, to drive out all the Air from a large <I>Æolipile,</I> I ea$ily $u$pected that the di$ten$ion of the Bladder in our pneumatical Ve$$el, might proceed not from the Watery $teams that came out at the narrow mouth of the <I>Æolipile,</I> and had very much wetted the Bladder, but from the rarified Air which in that $ort of Ve$$els is wont for a good while together to come out with the rarified Water: and accordingly having reiterated the Experi- ment I found it very difficult (by rea- $on of the $hrinking of the Bladders (up- on their being heated) and of other impe- diments) to make it $o accurately as to de- duce from it, that Water may be rarified into true Air. <p>Again$t the four other above-mention'd Con$iderations, we cannot $pend time to frame Objections, but mu$t forth with proceed to the mention of tho$e things that $eem to argue that Air (at lea$t $uch as produc'd our bubbles) maybe gene- rated of Water and other Bodies. <p>Fir$t then we have found by Experi- ence that a vapid Air, or Water rarified into vapor, may at lea$t for a while emu- late the ela$tical power of that which is generally acknowledg'd to be true Air. <pb n=170> For if you take a good <I>Æolipile,</I> with a moderately $trong and $lender Neck, and filling it with Water, lay it upon quick Coals, you may after a while ob$erve $o great a pre$$ure by $ome of the parts con- tain'd in the <I>Æolipile</I> upon others, that the Water will $ometimes be thrown up into the Air above three or four Foot high; and if you then take the <I>Æolipile</I> almo$t red hot from off the Fire, you may perceive that the Water will for a longer time then one would ea$ily imagine con- tinue to be $pouted out in a violent Stream. And if there remains but little Water in the <I>Æolipile</I> when tis taken ve- ry hot from the Fire, immerfing the Neck of it into cold Water, you will finde, that after it begins to $uck in $ome Water, there will be made from time to time $tore of large bubbles in that Water where into the neck was plunged. Which bubbles $eem manife$tly to proceed from hence, that for a while the heat in the <I>Æ- olipile</I> continues $trong enough to rarifie part of the Water that is $uck'd in, and expel it in the form of Vapors through the Water incumbent on the Pipe. If al- $o when the <I>Æolipile</I> is almo$t full of wa- ter, and therefore can contain but little <pb n=171> Air; you hold a Coal or Brand in that $tream of Vapors that i$$ues out of the narrow mouth of it, you will finde this vapid or rorid Air, (if I may $o call it) to blow the Fire very $trongly and with a roaring noi$e. And that it be not $aid that 'tis by the external Air which the a- queous $teams drive before them, and not by the Steams them$elves, that the Bla$t is made and the Flame excited; it has been ob$erv'd, that by approaching the Coal or Brand almo$t to the mouth of the <I>Æolipile,</I> the winde appear'd more vehement then if the Body to be kindled were held $ome Inches off. <p>But in regard the ela$tical power of the Stream, i$$uing out of an <I>Æolipile,</I> $eems manife$tly due to the heat that expands and agitates the aqueous Particles where- of that Stream con$i$ts, and that $uch rapid winds $eem to be but water $catter'd into little parts and $et a moving; $ince we finde, that holding a Knife, or any $olid, $mooth and clo$e Body again$t the $tream that i$$ues out of the Æolipile, the vapors conden$ing upon it, will pre$ently cover it with water: It will be very per- tinent to $ubjoyn a notable Experiment that I remember I have met with in the <pb n=172> de$cription given us by the Indu$trious <I>Kircher,</I> of $everal Mu$ical Engines. And (though it may $eem $omewhat prolix) we will recite what he delivers in his own words, which are the$e. <p><I>Cum codem tempore quo hæc $crip$i</I> <MARG><I><*>: Art: Mag: Cun: & Di$$on: <*>.</I> 9. <*> 309.</MARG> <I>$ummi Pont: Innocentii</I> X<SUP>mi</SUP> <I>mandato or- gani hydraulici in horto Quirinali con$ti- tuendi cur a mihi commendata e$$et; Æoliam camer am in$igni $ane $ucce$$u con$trui ju$si- mus, eá quæ $equitur ratione.</I> <p><I>Erat longitudo $ive altitudo cameræ</I> AH 5 <I>Pedum, Latitudine</I> 3 <I>fere ex lateribus</I> <MARG><I>See the fif- <*> Fi- gure,</I></MARG> <I>con$tructa; in medio duo tenebat Diaphrag- mata</I> CD <I>&</I> EJ <I>in modum cribri pluri- bus for aminibus pertu$a. Paulo infra ca- nalis</I> G <I>aquam advehens in$erebatur in</I> H <I>eidem epi$tomium par ab at exitum. Aqua it áque per canalem</I> G <I>maximo impetu ruens vehementi$simum ventum mox intus exci- t ab at; qui ventus nimia humiditate imbu- tus, ut purior exiret $iccior&queacute;, Diaphrag- mata ill a in cribri modum pertu$a, or dinata $unt. Intra hæc enim aquæ vehemens agi- tatio rupta fracta&queacute; aerem puriorem per</I> A <I>canalem $ubtilioremque emittebat: Verum cum po$tea inventũ $it aer&etilde; plus æquo humi- dũ interioribus Organi meatibus maximũ detrimentum inferre: Hinc ut aer aquo$us</I> <pb n=173> <I>$icci$simam cõ$i$tentiam acquireret, ordina- vimus canalem plumbeum</I> QR <I>in helicem contortum va$i</I> S <I>aliquantulum capaciori in modum Urnæ efformato, in$ertum. Intra urnam enim plumbeam & canalem tortuo- $um illi$us aer humidus, it a ab omni aquo$i- tate defæcabatur, ut ex furno in Organum derivatus dici potuerit. Urna</I> S <I>canalis tortuo$us</I> QR <I>ultimum orificium</I> Q <I>in$e- ritur anemothecæ organi. Et hunc modum organis hydraulicis omniũ apti$simũ reperi.</I> <p><I>Debet autem cameræ illa $ituari in loco quantum fieri pote$t $icciori it a ut longo ca- nali aqua intr a eam derivetur ne locus hu- miditate $ua Organis officiat.</I> <p>Thus far the Ingenious <I>Kircherus,</I> whom I the rather cite, becau$e although I have been informed of divers Ventiducts (as they call them) by very knowing Tra- vellers that have ob$erv'd them: Yet this relation of our Author being very pun- ctual, and deliver'd upon his own particu- lar Experience, has, I confe$s, made me wi$h I had had the good fortune when I was at <I>Rome,</I> to take notice of the$e Or- gans; or that I had now the opportunity of examining of $uch an Experiment. For if upon a $trict inquiry I $hould find that the breath that blows the Organs <pb n=174> does not really upon the cea$ing of its un- u$ual agitation by little and little relap$e into water, I $hould $trongly $u$pect that 'tis po$$ible for Water to be ea$ily turn'd into Air. I remember indeed, that we have formerly taught that there lurks an inter$per$ed Air in the pores of ordinary Water, which may po$$ibly be $truck out by the breaking of the Water in its fall into the Æolian Chamber, (as he calls it.) But in regard the Scheme $eems to repre- $ent that Chamber as clo$ely $hut, and thereby forbids us to $uppo$e that any Air is carried into it but what is latitant in the Water, it will $carce $eem probable to him who remembers how $mall a propor- tion of Air, that appear'd to be when its rarification $ea$ed, which was conceal'd in the Water we freed from bubbles in our Receiver, that $o little Air as is common- ly di$per$'d through Water, $hould be a- ble, in $o little Water as was requi$ite for $o $mall a room, to make $o vehement a Wind as our Author here tells us of. I have $ometime therefore $u$pected, that in this ca$e the Wind may be produc'd by $mall particles of the water it $elf, forci- bly expell'd out of the Chamber into the Organs. And to the Objection to which <pb n=175> I fore$aw this ghe$s to be liable, namely, That, no heat intervening, there appear'd nothing that $hould rai$e the Water into exhalations and give them an impul$e. I thought it might be $aid that motion a- lone, if vehement enough, may, with- out $en$ible heat, $uffice to break Water into very minute parts, and make them a$- cend upwards, if they can no where el$e more ea$ily continue their agitation. For Iremember, that Travelling betwixt <I>Ly- ons</I> and <I>Geneva,</I> I $aw, not very far out of the Way, a place where the River of <I>Rhone</I> coming $uddenly to be $treighten'd betwixt two Rocks, $o near each other, that a Man may (if my Memory fail me not) $tand a$tride upon both at once: that rapid Stream da$hing with great impetuo- $ity again$t its Rocky Boundaries, does break part of its Water into $uch minute Corpu$cles, and put them into $uch a mo- tion, that Pa$$engers ob$erve at a good di- $tance off, as it were a Mi$t ari$ing from that place, and a$cending a good way up into the Air. Such, I $ay, was my $u$- picion touching the Wind we have been con$idering, but it $eems $omething odde that aqueous Vapors $hould, like a dry Wind, pa$s through $o long and tortu- <pb n=176> ous a Pipe of Lead, as that de$crib'd by our Author, $ince we $ee in the Heads of Stills, and the Necks of <I>Æolipiles,</I> how quickly $uch vapors are even by a very lit- tle cold reconden$ed into Water. But to this al$o $omething may be $peciou$ly reply'd; wherefore contenting my $elf to have mention'd our Authors Experiment as a plau$ible, though not demon$trative proof, that Water may be tran$muted in- to Air. We will pa$s on to mention in the third place another Experiment, which we try'd in order to the $ame enquiry. <p>We took a clear Gla$s bubble (capable of containing by ghe$s about three Oun- ces of Water) with a Neck $omewhat long and wide, of a Cylindrical form; this we fill'd with Oyl of Vitriol and fair water, of each almo$t a like quantity, and ca$ting in half a dozen $mall Iron Nails, we $topt the mouth of the Gla$s (which was top-full of Liquor) with a flat piece of <I>Diapalma</I> provided for the purpo$e, that accommodating it $elf to the $urface of the water, the Air might be exqui- $itely excluded: and $peedily inverting the Viol, we put the Neck of it into a $mall wide-mouth'd Gla$s that $tood rea- dy with more of the $ame Liquor in it, to <pb n=177> receive it. As $oon as the neck had reach'd the bottom of the Liquor it was dipp'd into, there appear'd at the upper part (which was before the bottom) of the Viol a bubble, of about the bigne$s of a Pea, which $eem'd rather to con$i$t of $mall and recent bubbles, produc'd by the action of the di$$olving Liquor upon the Iron, then any parcel of the external Air that might be $u$pected to have got in upon the inver$ion of the Gla$s, e$peci- ally $ince we gave time to tho$e little Particles of Air which were carried down with the Nails into the Liquor to fly up again. But whence this fir$t bubble was produced, is not $o material to our Expe- riment, in regard it was $o $mall: For $oon after we perceiv'd the bubbles produced by the action of the <I>Men- $truum,</I> upon the Metal a$cending co- piou$ly to the bubble already named, and breaking into it, did $oon exceedingly in- crea$e it, and by degrees depre$s the wa- ter lower and lower, till at length the $ub- $tance contain'd in the$e bubbles po$$e$$ed the whole cavity of the Gla$s Viol, and almo$t of its Neck too, reaching much lower in the Neck then the $urface of the ambient Liquor, wherewith the open- mouth'd Gla$s was by this means almo$t <pb n=178> repleni$hed. And becau$e it might be $u$pected that the depre$$ion of the Li- quor might proceed from the agitation whereinto the exhaling and impri$on'd $teams were put, by that heat which is wont to re$ult from that action of corro- $ive $alts upon Metals, we $uffered both the Viol and the open-mouthed Gla$s to remain as they were, in a Window, for three or four days and nights together; but looking upou them $everal times during that while, as well as at the expiration of it, the whole cavity of the Gla$s bubble, and mo$t of its Neck, $eem'd to be po$- $e$$'d by Air, $ince by its $pring it was a- ble for $o long to hinder the expell'd and ambient Liquor from regaining its former place. And it was remarkable, that ju$t before we took the Gla$s bubble out of the other Gla$s, upon the application of a warm hand to the convex part of the bubble; the Impri$on'd $ub$tance readily dilated it $elf like Air, and broke through the Liquor in divers bubbles, $ucceeding one another. <p>Having al$o another time try'd the like Experiment with a $mall Viol, and with Nails di$$olv'd in <I>Aquafortis,</I> we found nothing incongruous to what we have now deliver'd. And this Circum$tance <pb n=179> we ob$erv'd, that the newly generated $teams did not onely po$$e$s almo$t all the whole cavity of the Gla$s, but divers times without the a$$i$tance of the heat of my hand, broke away in large bubbles through the ambient Liquor into the o- pen Air: So that the$e Experiments with corro$ive Liquors, $eem'd manife$t- ly enough to prove, though not that Air may be generated out of the Water, yet that in general air may be generated anew. <p>La$tly, to the foregoing Arguments from Experience we might ea$ily $ubjoyn the Authority of <I>Ari$totle,</I> and of (his followers) the Schools who are known to have taught, that Air and Water being Symbolizing Elements (in the quality of moi$ture) are ea$ily tran$mutable into one another. But we $hall rather to the fore- going Argument adde this, drawn from Rea$on, That if, as <I>Leucippus, Democri- tus, Epieurus</I> and others, follow'd by divers modern Naturali$ts, have taught, the difference of Bodies proceeds but from the various Magnitudes, Figures, Motions, and Textures of the $mall parts they con$i$t of, (all the quali- ties that make them differ, being de- ducible from thence) there appeares <pb n=180> no rea$on why the minute parts of Wa- ter, and other Bodies, may not be $o agi- tated or connected as to de$erve the name of Air. For if we allow the <I>Carte$ian Hypothe$is,</I> according to which, as we no- ted at the beginning of this Letter, the Air may con$i$t of any terrene or aqueous Corpu$cles, provided they be kept $wim- ming in the interfluent Cele$tial Matter; it is obvious that Air may be as often ge- nerated, as Terre$trial Particles minute enough to be carried up and down, by the Cele$tial Matter a$cend into the Atmo- $phere. And if we will have the Air to be a <I>congeries</I> of little $lender Springs, it $eems not impo$$ible, though it be diffi- cult, that the $mall parts of divers Bo- dies may by a lucky concour$e of cau$es be $o connected as to con$titute $uch little Springs, $ince (as we note in another Treati$e) Water in the Plants it nouri$hes is u$ually contriv'd into Springy Bodies, and even the bare alter'd po$ition and con- nexion of the parts of a Body may $uf- fice to give it a Spring that it had not be- fore, as may be $een in a thin and fiexible Plate of Silver; unto which, by $ome $troaks of a Hammer, you may give a Spring, and by onely heating it red hot <pb n=181> you may make it again flexible as be- fore. <p>The$e, My Lord, are $ome of the Con$iderations at pre$ent occurring to my thoughts, by which it may be made probable that Air may be generated a- new. And though it be not impo$$ible to propo$e Objections again$t the$e, as well as again$t what has been repre$ented in favor of the contrary Doctrine; yet having already almo$t tyr'd my $elf, and I fear more then almo$t tyr'd Your Lord- $hip with $o trouble$ome an Enquiry af- ter the Nature of bubbles, I $hall wil- lingly leave Your Lord$hip to judge of the Arguments alledged on either $ide, and I $hould $carce have ventur'd to enter- tain You $o long concerning $uch empty things as the Bubbles, which have occa- $ion'd all this Di$cour$e, but that I am willing to invite You to take notice with me of the ob$curity of things, or the dim- ne$s of our created Intellects (which yet of late too many $o far pre$ume upon, as either to Deny or Cen$ure the Almighty and Omni$cient Creator him$elf) and to learn hence this Le$$on, That there are very many Things in Nature that we di$- dainfully over-look as obvious or de$pi- <pb n=182> cable, each of which would exerci$e our Under$tandings, if not po$e them too, if we would but attentively enough con$ider it, and not $uperficially contemplate, but attempt $atisfactorily to explicate the na- ture of it. <p>SInce the writing of the twenty one and <MARG><I>Experi- ment</I> 23.</MARG> twenty $econd Experiments (and not- with$tanding all that hath been on their occa$ion deliver'd concerning bubbles) we made $ome further tryals in pro$ecution of the $ame inquiry whereto they were de$igned. <p>We cho$e then, among$t tho$e Gla$$es which Chymi$ts are wont to call Philo$o- phical Eggs, one that containing about nine Ounces of Water, had a Neck of half an Inch in Diameter at the top, and as we ghe$t, almo$t an Inch at the bot- tom; which breadth we pitch'd upon for a rea$on that will by and by appear: then filling it with common Water to the height of about a Foot and a half, $o that the upper part remain'd empty, we $hut it into the Receiver, and watch'd what would follow upon pumping, which pro- <pb n=183> ved that a great part of the Air being drawn out, the bubbles began to di$cover them$elves at the bottom and $ides of the Gla$s; and increa$ing, as the Air was more and more drawn away, they did from time to time a$cend copiou$ly e- nough to the top of the Water, and there quickly break: but by rea$on that the widene$s of the Gla$s allow'd them free pa$$age through the Water, they did not appear as in the former Experiments to make it $well: The Water $carce ever ri- $ing at all above the mark affixt to its up- per $urface when it was put in, and upon the return permitted to the outward Air, and con$equently the $hrinking in of the remaining bubbles, the Water $eem'd to have lo$t of its fir$t extent, by the avo- lation of the formerly inter$per$'d Air. <p>Being willing likewi$e to try whether di$tilled Water were by having been di- vided into minute parts, and then re-uni- ted, more or le$s di$po$'d to expand it $elf then Water not di$till'd: We took out of our Laboratory $ome careful- ly di$till'd Rain-water, and put about two Ounces of it into a round Gla$s <pb n=184> bubble with a very $mall Neck (not ex- ceeding the $ixth part of an Inch in Dia- meter) which we fill'd half way to the top, and then convey'd it into the Recei- ver; the i$$ue was, That though we drew out more then ordinary, yet there ap- pear'd not the lea$t intume$cence of the Water, nor any a$cending bubbles. <p>But $u$pecting that either the $mall quantity of the water or the Figure of the Ve$$el might have an intere$t in this odde <I>Phænomenon,</I> we took the lately mention'd Philo$ophical Egge, and another not much differing from it; the former we fill'd up with di$till'd Rain-water to the old mark, and into the latter we put a long Cylinder or Rod of $olid Gla$s to $treighten the cavity of the Neck by al- mo$t filling it up; and then pouring $ome di$tilled Water into that al$o, till it reach'd within $ome Fingers breadth of the top, the Eggs were let down into the Receiver. In this Experiment the Air was $o far drawn forth before there ap- pear'd any bubble in either of the Gla$$es, that the di$parity betwixt this and com- mon water was manife$t enough. But at length, when the Air was almo$t quite pump'd out, the bubbles began to di$- <pb n=185> clo$e them$elves, and to increa$e as the pre$$ure of the Air in the Receiver de- crea$'d. But whereas in the fir$t men- tion'd Philo$ophical Egge the bubbles were very $mall, and never able to $well the Water, that we took notice of, at all above the mark: In the other, who$e Neck, as we lately $aid, was $traightned, and their pa$$age ob$tructed, great num- bers of them, and bigger, fa$tned them- $elves to the lower end of the Gla$s ram- mer (if we may $o call it) and gather'd in $uch numbers between that and the $ides of the Neck, that the Water $well'd a- bout a Fingers breadth above the mark, though upon the admitting of the exter- nal Air it relap$'d to the former mark, or rather fell $omewhat below it. And al- though thereupon in the fir$t nam'd Ve$- $el all the bubbles pre$ently di$-appear'd, yet in the other we ob$erv'd, that divers remained fa$tned to the lower part of the Gla$s rammer, and continued there $ome- what to our wonder, for above an hour after, but contracted in their Dimen- $ions. <p>Moreover, having $uffered the Gla$$es to remain above twenty four hours in the <pb n=186> Receiver, we afterwards repeated the Ex- periment, to try what change the ex$ucti- on of the external Air would produce in the Water, after the internal and latitant Air had (as is above recited) in great mea- $ure got away in bubbles, and whether or no the Water would by $tanding re-admit any new particles of Air in the room of tho$e that had for$aken it. But though we exhau$ted the Receiver very diligent- ly, yet we $carce $aw a bubble in either of the Gla$$es; notwith$tanding which, we perceiv'd the Water to ri$e about the breadth of a Barly-corn, or more, in the Neck of that Gla$s wherein the $olid Cy- linder had been put; The Liquor in the other Gla$s not $en$ibly $welling. <p>And la$tly, upon the letting in of the Air, the Water in the $traightned Neck $oon $ub$ided to the mark above which it had $wollen, which whether it ought to be a$crib'd to the $ame $mall expan$ion of the parts of the Water it $elf, or to the rarifaction of $ome yet latitant Air broken into $uch $mall particles, as to e- $cape our ob$ervation, $eems not ea$ily determinable, without $uch further tryals, as would perhaps prove tedious to be re- cited as well as to be made; though I was <pb n=187> content to $et down tho$e already men- tion'd, that it might appear how requi- $ite it is in nice Experiments to con$ider variety of Circum$tances. <p>AFter having thus di$cover'd what ope- <MARG><I>Experi- ment</I> 24.</MARG> ration the ex$uction of the ambient Air had upon Water, we thought good to try al$o what changes would happen in other Liquors upon the like taking off the pre$$ure of the external Air. We took then a Gla$s Egge, $omewhat bigger then a Turkey Egge, which had a long Neck or Stem of about a 1/3 part of an Inch in Diameter; and filling it up with Sallet Oyl until it reach'd above half way to the top of the Neck, we inclo$'d it in the Re- ceiver together with common Water in a re$embling Ve$$el, that we might the better compare together the operation of the ex$uction of the Air upon tho$e two Liquors. The Pump being $et a work there began to appear bubbles in the Oyl much $ooner then in the Water, and afterwards they al$o a$cended much more copiou$ly in the former Liquor then the latter: Nay, and when by having quite tired the Pum- per, and almo$t our own patience, we <pb n=188> gave over, the bubbles ri$e almo$t (if not altogether) in as great numbers as ever, in$omuch as none of the various Liquors we tryed either before or $ince, $eem'd to abound more with Aerial Parti- cles then did this Oyl. In which it was further remarkable, that between the time it was $et into the Receiver, and that at which we could get ready to Pump, it $ub- $ided notably (by ghe$s about half an Inch) below the mark it reach'd before it was put in. <p>After this expre$$'d Oyl, we made tryal of a di$till'd one, and for that purpo$e made choice of the common Oyl or Spi- rit (for in the Shops where it is $old, the $ame Liquor is promi$cuou$ly call'd by ei- ther name) of Turpentine; becau$e 'twas onely of that Chymical Oyl, we had a $ufficient quantity: which, being put in- to a $mall Gla$s bubble with a $lender Neck, $o as to fill it to about two Inches from the top, did, upon the evacuating of the Receiver, pre$ent us with great $tore of bubbles; mo$t of which ri$ing from the bottom, expanded them$elves exceedingly in their a$cent, and made the Liquor in the Neck to $well $o much by degrees, that at length it divers times ran <pb n=189> over at the top: by which means, we were hindred from being able to di$cern upon the letting in of the Air, how much the $ub$idence of the Oyl below the fir$t mark was due to the rece$s of the bub- bles. <p>Having likewi$e a minde to try whe- ther as $trong a $olution of Salt of Tartar in fair Water as could be made (we ha- ving then no Oyl of Tartar <I>per deliqui- um</I> at hand) though it be accounted, Quick-$ilver excepted, the heavie$t of Liquors would afford us any bubbles; we put in a Gla$s Egge full of it at the $ame time, with other Liquors, and found that they did long yield $tore of bubbles be- fore any di$covered them$elves in the Liquor of Tartar; and having pur$ued the Experiment, it appear'd, That of all the Liquors we made tryal of, this afford- ed the fewe$t and the $malle$t Bubbles. <p>Spirit of Vinager being try'd after the $ame manner, exhibited a moderate num- ber of bubbles, but $carce any thing el$e worth the mentioning. <p>Nor could we in red Wine, try'd in a Gla$s Egge, take notice of any thing ve- ry ob$ervable. For though upon the ex- $uction of the Air the bubbles a$cended <pb n=190> in this Liquor, as it were in $holes, and $hifted places among them$elves in their a$cent; yet the Intume$cence of the whole bulk of the Liquor was $carce at all $en$ible, the bubbles mo$t commonly breaking very $oon after their arrival at the top, where during their $tay, they compo$'d a kinde of $hallow froth, which alone appear'd higher in the Neck of the Gla$s, then was the Wine when it was fir$t let down. Neither yet did Milk, con- vey'd into our Pneumatical Ve$$el, pre- $ent us with any thing memorable, $ave that (as it $eem'd by rea$on of $ome un- ctuou$ne$s of the Liquor) the bubbles not ea$ily breaking at the top, and thru$t- ing up one another made the intume$cence appear much greater then that of common Water. <p>We likewi$e convey'd Hens Eggs into the Receiver, but, after the ex$uction of the Air, took them out whole again. That which invited us to put them in, was, That (as perhaps we mention in other Papers) we had among other Experiments of cold, made Eggs bur$t, by freezing them within doors with Snow and Salt: The Ice, into which the aqueous parts of the Egge were turned by the cold, $o di$tend- <pb n=191> ing (probably by rea$on of the numerous bubbles wont to be ob$ervable in Ice) the outward parts of the Egge, that it u$ually crack'd the $hell, though the inner Mem- brane that involv'd the $everal Liquors of the Egge, becau$e it would $tretch and yield, remain d unbroken, And here- upon we imagin'd that in our Engine it might appear whether or no there were any con$iderable Spring, either in any of the Liquors, or in any other more $piri- tuous $ub$tance included in the Egge. <p>We took al$o $ome Spirit of Urine, carele$ly enough deflegmed, and put it in- to the $ame Gla$s (fir$t carefully $cowr'd and clean$'d) wherein we had put the Oyl- olive above mention'd: We took al$o an- other Gla$s, differing from a Gla$s Egge, onely in that its bottom was $lat, and fill'd it up to about 2/3 of the Neck (which was wider then that of the Egge) with rectifi- ed Spirit of Wine. <p>We took al$o another Gla$s Egge, and having fill'd it with common Water till it reach'd to the middle of the Neck, we pour'd to it of the $ame Spirit of Wine, till it reach'd about an Inch higher. <p>The$e three Gla$$es having marks $et on them, over again$t the edges of the <pb n=192> contain'd Liquors were put into the Re- ceiver, and that beginning to be evacua- ted, the bubbles in all the three Liquors began to appear. The mixture of the Spirit of Wine and Water di$clo$'d a great $tore of bubbles, e$pecially towards the top; but $carce afforded us any thing worth remem bring. The Spirit of Urine appear'd to $well near an Inch and an half above the mark; and be$ides that, $ent forth $tore of bubbles, which made a kinde of froth at the upper part of it. And above that $pume there appear'd eight or ten great bubbles one above another, in a very decent order, each of them con$titu- ting, as it were, a Cylinder of about half an Inch high, and as broad as the internal cavity of the Neck: So that all the upper part of the Neck (for the$e bubbles reach'd to the top) $eem'd to be divided into al- mo$t equal parts, by certain Diaphrag- mes, con$i$ting of the coats of the bub- bles, who$e edges appear'd like $o many Rings $u$pended one above another. <p>In the Spirit of Wine there did ari$e a great multitude of bubbles, even till wearine$s did make us give over the Ex- periment. And in the$e bubbles two or three things were remarkable; as fir$t, <pb n=193> That they a$cended with a very notable celerity: Next, That being arriv'd at the top, they made no $tay there, and yet, notwith$tanding the great thinne$s and $pitituou$ne$s of the Liquor, did, before they broke, lift up the upper $urface of it, and for a moment or two form thereof a thin film or skin which appear'd protu- berant above the re$t of the $uperficies like a $mall Hemi$phere. Thirdly, That they a$cended $traight up, whereas tho$e produc'd at the lower part of the Ve$$el, containing the mixture of the Water and Spirit of Wine, a$cended with a waver- ing or wrigling motion, whereby they de$crib'd an indented Line. La$tly, It was ob$ervable in the Spirit of Wine (and we took notice of the like in the Oyl of Turpentine lately mention'd) that not onely the bubbles $eem'd to ri$e from cer- tain determinate places at the bottom of the Gla$s, but that in their a$cen$ion they kept an almo$t equal di$tance from each other, and follow'd one another in a cer- tain order, whereby they $eem'd part of $mall Bracelets, con$i$ting of equally lit- tle incontiguous Beads: the lower end of each Bracelet, being as it were, fa$ten'd to a certain point at the bottom of the Gla$s. <pb n=194> <p>The Air being $paringly let into the Receiver, the great bubbles formerly mention'd as incumbent upon one ano- ther, in that Gla$s that contain'd the Spi- rit of Urine, were by orderly degrees le$$en'd, till at length they wholly $ub$i- ded, notwith$tanding the rece$s of $o ma- ny bubbles as broke on the top of the Spirit of Urine, during all the time of the Experiment; yet it $carcely appear'd at all to be $unk below the mark: Nor did the mixture of Spirit of Wine and Water con$iderably $ub$ide. But that is no- thing to what we ob$erv'd in the Spirit of Wine, for not onely it con$picuou$ly expanded it $elf in the Neck of the Ve$$el that contain'd it, notwith$tand- ing the largene$s of it; and that the bubbles were about to break at the top of it almo$t a$$oon as they arriv'd there: but upon the re-admi$$ion of the external Air, the Spirit of Wine retain'd its newly acquired expan$ion. And though we let it alone for near an hour together, in expectation that it might $ub$ide; yet when we took it out, we found it $till $well'd between a quarter and half an Inch above the mark; and although it was not ea$ily <pb n=195> imaginable how this <I>Phænomenon</I> could proceed from any mi$take in trying the Experiment, yet the $trangene$$e of it invited me to repeat it with fre$h Spirit of Wine; which, $welling in the Neck as formerly, I left all Night in the Receiver, allowing free acce$s to the external Air at the Stop-cock, and the next day found it $till expanded as be- fore, $ave that it $eem'd a little lower: which decrement perhaps proceeded from the avolation of $ome of the fugitive parts of $o volatile a Liquor. And for better $atisfaction having taken out the Gla$s, and con$ider'd it in the open Air, and at a Window, I could not finde that there was any remaining Bubbles that could occa$ion the per$evering and ad- mir'd expan$ion. <p>BEing de$irous to di$cover what diffe- <MARG><I>Experi- ment</I> 25.</MARG> rence there might be as to gravity and levity, between Air expanded under Wa- ter, and it $elfe before $uch expan$ion; we took two very $mall Viols, $uch as Chy- mical E$$ences (as they call them) are wont to be kept in, and of the $ize and $hape ex- pre$$ed by the 8<SUP>th</SUP> Figure: into one of the$e <pb n=196> we put $o much of a certain ponderous Mercurial mixture (hapning to be then at hand) that the mouth being $topt with a little $oft Wax, the Gla$s would ju$t $ink in Water and no more; this we let fall to the bottom of a wide-mouth'd Cry$tal Jar, fill'd with about half a pint of com- mon Water, and into the $ame Ve$$el we $unk the other E$$ence Gla$s un$topp'd, with as much Water in it as was more then $ufficient to make it $ub$ide. Both the$e $unk with their mouthes downward, the former being about three quarters full of Air, the latter containing in it a bub- ble of Air that was ghe$$'d to be of the bigne$s of half a Pea: This done, the wide-mouth'd Gla$s was let down into the Receiver, and the way of imploy- ing the Engine was carefully made u$e of. <p>The $ucce$s was, That having drawn out a pretty quantity of Air, the bubbles began to di$clo$e them$elves in the Wa- ter, as in the former Experiments; and though for a good while after the bubbles a$cended in $warms from the lower parts of the Water, and ha$tily broke at the top; yet we pro$ecuted the Experiment $o long without $eeing any effect wrought <pb n=197> upon the E$$ence: Bottles, that we began to di$pair of $eeing either of them ri$e, but continuing to ply the Pump, that little Gla$s, who$e mouth was open'd, came to the top of the Water, being, as it were, boy'd up thither by a great number of bubbles that had fa$tned them$elves to the $ides of it; $wimming thus with the mouth downward, we could ea$ily per- ceive that the internal Air above men- tion'd had much delated it $elf, and there- by $eem'd to have contributed to the e- merging of the Gla$s, which remain'd floating, notwith$tanding the breaking and vani$hing of mo$t of the contiguous bubbles: being hereby incouraged to per- $i$t in pumping, we ob$erved with $ome plea$ure, that at each time we turn'd the Key, the Air in the little Gla$s did mani- fe$tly expand it $elf and thru$t out the wa- ter, generally retaining a very protuberant $urface where it was contiguous to the re- maining Water. And when after divers ex$uctions of the Air in the Receiver, that in the little Viol $o dilated it $elf as to expel almo$t all the Water, it turn'd up its mouth towards the $urface of the Water in the Jar, and there deliver'd a large bubble, and then relap$ed into its <pb n=198> formér floating po$ture: And this Expe- riment taught us, among other things, that it was a work of more time and la- bor then we imagin'd, to exhau$t our En- gine as much as it may be exhau$ted: for although before the emerging of the $mall Viol, we did (as has been touch'd alrea- dy) think we had very con$iderably em- ptyed the Receiver, becau$e there $eem'd to come out but very little or almo$t no $en$ible Air at each ex$uction into and out of the Cylinder; yet after- wards, at each drawing down the Suc- ker, the Air included in the Viol did manife$tly dilate it $elf, $o long, that it did no le$s then nine times turn its mouth upwards, and di$charge a bub- ble by conjecture about the bigne$s of a Pea, after the manner newly recited. But as for that Violl which had the weight in it, it ro$e not at all. So that being not able by quick pumping to gain another bubble from the Air in the $wimming Gla$s, which proceed- ed from $ome $mall leak in the Ve$$el, though it held in this Experiment more $tanch then was u$ual, we thought fit to let in lea$urely the Air from with- out, upon who$e admi$$ion that with- <pb n=199> in the Viol $hrinking into a very nar- row compa$s, the Gla$s did, as we expe- cted, fall down to the bottom of the Jar. <p>But being de$irous before we proceed- ed to any new. Experiment, to try once more whether the little Gla$s that had the weight in it might not al$o be rai$'d. After we had $uffer'd the Engine to re- main clo$'d as it was, for five or $ix hours, the Pump was again ply'd with $o much ob$tinacy, that not onely a- bout the upper part of the Jar there ap- pear'd a good number of bubbles (but very much $maller then tho$e we $aw the fir$t time) but afterwards there came from the bottom of the Jar, bub- bles about the bigne$s of $mal Peas: which the Pump being $till kept going, fol- low'd one another, to the number of forty, coming from the $topp'd Violl; who$e mouth, it $eems, had not been $hut $o $trongly and clo$ely, but that the included Air, dilating it $elf by its own $pring, made it$elf $ome little pa$$age betwixt the Wall and the Gla$s, and got away in the$e bub- bles; after which, the un$topp'd Gla$s be- gan to float again, the Air $hut up in it <pb n=200> being manife$tly $o dilated as to expel a good part of the Water, but not $o much as to break quite thorow. And at length, when our expectation of it was almo$t ti- red out, the heavier of the two Viols be- gan to come aloft, and immediately to $ub$ide again, which appear'd to be oc- ca$ion'd by the Air within it, who$e bulk and $pring being weaken'd by the rece$s of the forty bubbles before-mention'd, it was no longer able, as formerly, to break forcibly through the incumbent Water; but forming a bubble at the mouth of the Gla$s, boyed it up towards the top, and there getting away, left it to $ink again till the pre$$ure of the Air in the Recei- ver being further taken off, the Air in the Viol was permitted to expand it $elf fur- ther, and to create another bubble, by which it was again for a while carried up. And it was remarkable, that though after having emptyed the Receiver as far as well we could, we cea$'d from pumping; yet the Ve$$el continuing more $tanch then it was wont, this a$cent and fall of the Viol was repeated to the ninth time; the included Air, by rea$on of the $mal- ne$s of the vent at which it mu$t pa$s out, being not able to get away otherwi$e then <pb n=201> little by little; and con$equently, in divers $uch parcels as were able to con$titute bubbles, each of them big enough to rai$e the Viol and keep it aloft until the avolation of that bubble. Whereby it may appear, that the grand rule in <I>Hy- dro$taticks,</I> That a Body will $wim in the Water, in ca$e it be lighter then as much of that Water that equals it in bulk, will hold likewi$e when the pre$$ure of the At- mo$phere is in very great mea$ure, if not when it is totally taken off from the Li- quor and the Body: though it were worth inquiring what it is that $o plentifully concurs to fill the bubbles made in our Experiment by the $o much expanded Air, for to $ay with the old Peripatetick Schools, That the Air, in Rarefaction, may acquire a new extent, without the admi$$ion of any new $ub$tance, would be an account of the <I>Phænomenon</I> very much out of date, and which, I $uppo$e, our Modern Naturali$ts would neither give, nor acquie$s in. <p>I know not whether it may be requi$ite to adde, that in this Experiment, as in the former, the outward Air being let in did $oon precipitate the floating Viol. But I think it will not be ami$s to note, that <pb n=202> (congruou$ly to what hath been above recorded of the va$t expan$ion of the Air) the Water which in the heavier Viol $uc- ceeded in the room of tho$e forty odde, if not fifty great bubbles of Air, which at $everal times got out of it, amounted but to a very incon$iderable bigne$s. <p>IT having been ob$erv'd by tho$e that <MARG><I>Experi- ment</I> 26.</MARG> have con$ider'd what belongs to <I>Pendu- lums</I> (a Speculation that may, in my poor judgement, be highly u$eful to the Naturali$ts) that their Vibrations are more $lowly made, and that their moti- on la$ts le$s in a thicker, then in a thinner Medium: We thought it not ami$s to try if a <I>Pendulum</I> would $wing fa$ter, or continue $winging longer in our Receiver, in ca$e of the ex$uction of the Air, then otherwi$e. Wherefore we took a couple of round and poli$h'd <I>Pendulums</I> of Iron or Steel, of equal bigne$s, as near as we could get the Artificer to make them, and weighing each of them twenty Dragmes, wanting as many Grains. One of the$e we $u$pended in the cavity of the Recei- ver by a very $lender $ilken $tring, of a- bout $even Inches and a half in length <pb n=203> from the cover of the Receiver to which it was fa$ten'd. Then (by inclining the Engine) we made the <I>Pendulum</I> $wing too and fro in it, and de$crib'd as long Arches as in the capacity of $o brittle a Ve$$el we thought $afe and convenient. And one of the A$$i$tants telling the recur$ions of the other <I>Pendulum</I> hanging in the free Air, by a $tring of about the $ame length, we $horten'd and lengthen'd this other <I>Pen- dulum,</I> till it appear'd to keep the $ame pace in its Vibrations, with that $hut up in the Receiver. Then having carefully drawn away the Air, we did again $et the <I>Pendulum</I> in the Receiver a vibrating; and giving the other <I>Pendulum</I> $uch a mo- tion as made it de$cribe an Arch, accord- ing to ones ghe$s, equal to that of the in- cluded <I>Pendulum;</I> we reckon'd, one of us, the Recur$ions of that <I>Pendulum</I> which was $winging within the Receiver; and another of us that which was moving in (that which one would think a much more re$i$ting <I>medinm</I>) the Air. But once, one of us reckon'd near two and twenty Re- cur$ions of the included <I>Pendulum,</I> whil$t the other reckon'd but twenty of the <I>Pen- dulum</I> that vibrated without. And an- other time al$o, the former of the$e <I>Pen-</I> <pb n=204> <I>dula</I> was reckon'd to have made one and twenty Recur$ions, wherein the other made but twenty: Yet this Experiment $eem'd to teach us little, $ave that the dif- ference betwixt the motion of $uch a <I>Pen- dulum</I> in the common Air, and in one ex- ceedingly rarified, is $carce $en$ible in Ve$$els no bigger then our Receiver; e- $pecially $ince though during this Expe- riment it held very well, yet we could not $uppo$e it to be altogether devoid of Air. We ob$erv'd al$o, that when the Receiver was full of Air, the included <I>Pendulum</I> continu'd its Recur$ions about fifteen minutes (or a quarter of an hour) before it left off $winging; and that after the ex$uction of the Air, the Vibration of the $ame <I>Pendulum</I> (being fre$h put in- to motion) appear'd not (by a minutes Watch) to la$t $en$ibly longer. So that the event of this Experiment being other then we expected, $carce afforded us any other $atisfaction, then that of our not having omitted to try it. And whether in ca$e the tryal be made with a <I>Pendulum</I> much le$s di$proportionate to the Air then Steel is, the event will much better an- $wer expectation, experience may be con- $ulted. <pb n=205> <p>THat the Air is the medium whereby $ounds are convey'd to the Ear, has <MARG><I>Experi- ment</I> 27.</MARG> been for many Ages, and is yet the com- mon Doctrine of the Schools. But this Received Opinion has been of late op- po$'d by $ome Philo$ophers upon the ac- count of an Experiment made by the Indu$trious <I>Kircher,</I> and other Learned Men, who have (as they a$$ure us) ob- $erv'd, That if a Bell, with a Steel Clap- per, be $o fa$ten'd to the in$ide of a Tube, that upon the making the Experiment <I>De Vacuo</I> with that Tube, the Bell remain'd $u$pended in the de$erted $pace at the up- per end of the Tube: And if al$o a vi- gorous Load-$tone be apply'd on the out- $ide of the Tube to the Bell, it will at- tract the Clapper, which upon the Remo- val of the Load-$tone falling back, will $trike again$t the oppo$ite $ide of the Bell, and thereby produce a very audible $ound, whence divers have concluded, That 'tis not the Air, but $ome more $ub- tle Body that is the medium of $ounds. But becau$e we conceiv'd that, to invali- date $uch a con$equence from this ingeni- ous Experiment (though the mo$t lucife- <pb n=206> rous, that could well be made without $ome $uch Engine as ours) $ome things might be $peciou$ly enough alleadg'd; we thought fit to make a tryal or two, in or- der to the Di$covery of what the Air does in conveying of $ounds, re$erving divers other Experiments tryable in our Engine concerning $ounds, till we can obtain more lea$ure to pro$ecute them. Conceiving it then the be$t way to make our tryal with $uch a noi$e as might not be loud enough to make it difficult to di$cern $lighter va- riations in it, but rather might be, both la$ting, that we might take notice by what degrees it decrea$'d; and $o $mall, that it could not grow much weaker with- out becoming imperceptible. We took a Watch, who$e Ca$e we open'd, that the contain'd Air might have free egre$s into that of the Receiver. And this Watch was $u$pended in the cavity of the Ve$$el onely by a Pack-thred, as the unlikelie$t thing to convey a $ound to the top of the Receiver: And then clo$ing up the Ve$- $el with melted Plai$ter, we li$ten'd near the $ides of it, and plainly enough heard the noi$e made by the ballance. Tho$e al- $o of us, that watch'd for that Circum- $tance, ob$erv'd, that the noi$e $eem'd to <pb n=207> come directly in a $traight Line from the Watch unto the Ear. And it was ob$erva- ble to this purpo$e, that we found a mani- fe$t di$parity of noi$e, by holding our Ears near the $ides of the Receiver, and near the Cover of it: which difference $eem'd to proceed from that of the Texture of the Gla$s, from the $tructure of the cover (and of the Cement) through which the $ound was propagated from the Watch to the Ear. But let us pro$ecute our Experiment. The Pump after this being imployd, it $eemd that from time to time the $ound grew fainter and fainter; $o that when the Rec iver was empty'd as much as it u$'d to be for the foregoing Experiments, nei- ther we, nor $ome $trangers that chanc'd to be then in the room, could, by applying our Ears to the very $ides, hear any noi$e from within; though we could ea$ily per- ceive that by the moving of the hand which mark'd the $econd minutes, and by that of the ballance, that the Watch nei- ther $tood $til, nor remarkably varied from its wonted motion. And to $atisfie our $elvs further that it was indeed the ab$ence of the Air about the Watch that hinder'd us from hearing it, we let in the external Air at the Stop-cock, and then though we <pb n=208> turn'd the Key and $topt the Valve, yet we could plainly hear the noi$e made by the ballance, though we held our Ears $ome- times at two Foot di$tance from the out- $ide of the Receiver. And this Experi- ment being reiterated in another place, $ucceded after the like manner. Which $eems to prove, that whether or no the Air be the onely, it is at lea$t, the princi- pal medium of Sounds. And by the way it is very well worth noting, that in a Ve$- $el $o well clo$'d as our Receiver, $o weak a pul$e as that of the ballance of a Watch $hould propagate a motion to the Ear in a Phi$ically $traight Line, notwith$tanding the interpo$ition of $o clo$e a Body as Gla$s, e$pecially Gla$s of $uch thickne$s as that of our Receiver; $ince by this it $eems that the air impri$on'd in the Gla$s, mu$t, by the motion of the ballance, be made to beat again$t the concave part of the Receiver, $trongly enough to make its convex part beat upon the contiguous Air, and $o propagate the motion to the Li$tners ears. I know this cannot but $eem $trange to tho$e, who, with an emi- nent Modern Philo$opher, will not allow that a Sound, made in the cavity of a Room, or other place $o clo$'d, that there <pb n=209> is no intercour$e betwixt the external and internal Air, can be heard by tho$e with- out, unle$s the $ounding Body do imme- diately $trike again$t $ome part of the in- clo$ing Body. But not having now time to handle Controver$ies, we $hall onely annex, That after the foregoing Experi- ment, we took a Bell of about two Inches in Diameter at the bottom, which was $upported in the mid$t of the cavity of the Receiver by a bent $tick, which by rea$on of its Spring pre$$'d with its two ends again$t the oppo$ite parts of the in- $ide of the Ve$$el: in which, when it was clo$'d up, we ob$erv'd that the Bell $eem'd to $ound more dead then it did when ju$t before it $ounded in the open Air. And yet, when afterwards we had as formerly emptyed the Receiver, we could not di$- cern any con$iderable change (for $ome $aid they ob$erv'd a $mall one) in the loud- ne$s of the $ound, whereby it $eem'd that though the Air be the principal medium of $ound, yet either a more $ubtle mat- ter may be al$o a medium of it, or el$e an ambient Body that contains but very few particles of Air, in compari$on of tho$e it is ea$ily capable of, is $ufficient for that purpo$e. And this, among o- <pb n=210> ther things, invited us to con$ider, whether in the above-mention'd Experiment made with the Bell and the Load-$tone, there might not in the de$erted part of the Tube remain Air enough to produce a $ound: $ince the Tubes for the Experiment <I>De Vacuo</I> (not to mention the u$ual thin- ne$s of the Gla$s) being $eldom made greater then is requi$ite, a little Air might bear a not incon$iderable proportion to the de$erted $pace. And that al$o, in the Experiment <I>De Vacuo,</I> as it is wont to be made, there is generally $ome little Air that gets in from without, or at lea$t $tore of bubbles that ari$e from the Body of the Quick-$ilver, or other Liquor it $elf, Ob$ervations heedfully made have fre- quently informed us: And it may al$o appear, by what has been formerly deli- vered concerning the <I>Torricellian</I> Experi- ment. <p>On the occa$ion of this Experiment concerning $ounds, we may adde in this place, That when we try'd the Experiment formerly mention'd, of firing Gun-pow- der with a Pi$tol in our evacuated Recei- ver, the noi$e made by the $triking of the Flint again$t the Steel, was exceeding languid in compari$on of what it would <pb n=211> have been in the open Air. And on di- vers other occa$ions it appear'd that the $ounds created within our exhau$ted Gla$s, if they were not lo$t before they reach'd the Ear, $eem'd at lea$t to arrive there very much weaken'd. We intended to try whether or no the Wire-$tring of an In$trument $hut up into our Receiver, would, when the ambient Air was $uck'd out, at all tremble, if in another In$trument held clo$e to it, but without the Receiver a $tring tun'd (as Mu$icians $peak, how properly I now examine not) to an Uni$on with it, were briskly toucht, and $et a Vi- brating. This, I $ay, we purpo$'d to try to $ee how the motion made in the Air without, would be propagated through the cavity of our evacuated Receiver. But when the In$trument wherewith the tryal was to be made came to be imploy'd, it prov'd too big to go into the Pneumatical Ve$$el, and we have not now the conveni- ency to have a fitter made. <p>We thought likewi$e to convey into the Receiver a long and $lender pair of Bellows, made after the fa$hion of tho$e u$ually employ'd to blow Organs, and fur- ni$h'd with a $mall Mu$ical in$tead of an <pb n=212> ordinary Pipe. For we hop'd, that by means of a $tring fa$tned to the upper part of the Bellows, and to the moveable $topple that makes a part of the Cover of our Receiver, we $hould, by frequent- ly turning round that $topple, and the an- nexed $tring, after the manner already often recited, be able to lift up and di$tend the Bellows; and by the help of a com- petent weight fa$ten'd to the $ame upper part of the Bellows, we $hould likewi$e be able, at plea$ure, to compre$s them: and by con$equence, try whether that $ubtler matter then Air (which, accord- ing to tho$e that deny a <I>Vacuum,</I> mu$t be $uppo$'d to fill the exhau$ted Receiver) would be able to produce a $ound in the Mu$ical Pipe; or in a Pipe like that of or- dinary Bellows, to beget a Wind capable to turn or $et a moving $ome very light matter, either $hap'd like the Sails of a Wind-Mill, or of $ome other conveni- ent form, and expo$'d to its Orifice. This Experiment, I $ay, we thought to make, but have not yet actually made it for want of an Artificer to make us $uch a pair of Bellows as it requires. <p>We had thoughts al$o of trying whe- ther or no, as Sounds made by Bodies in <pb n=213> our Receiver become much more languid then ordinary, by rea$on of the want of Air, $o they would grow $tronger, in ca$e there were an unu$ual quantity of Air crouded and $hut up in the $ame Ve$$el, which may be done (though not without $ome difficulty) by the help of the Pump, provided the Cover and Stopple be $o firmly fa$ten'd (by binding and Cement, or otherwi$e) to the Gla$s; and to each other, that there be no danger of the conden$'d Airs blowing of either of them away, or its breaking through the jun- ctures. The$e thoughts, My Lord, as I was $aying, we entertain'd; but for want of lea$ure, as, of as good Receivers as ours, to $ub$titute in its place, in ca$e we $hould break it before we learn'd the skill of condencing the Air in it, we dur$t not put them in practice: Yet, on this occa- $ion, give me leave to adverti$e Your Lord$hip once for all, That though for the rea$ons newly intimated, we have, Onely in the $eventeenth Experiment, taken notice, that by the help of our En- gine the Air may be conden$'d as well as rarified; yet there are divers other of our Experiments, who$e <I>Phænomena</I> it were <pb n=214> worth while to try to vary, by means of the compre$$ion of the Air. <p>WE taught, among divers other <MARG><I>Experi- ment</I> 28.</MARG> things, when we di$cour$'d of our fir$t Experiment, That the Air $hut up in our Receiver, pre$$eth as $trongly upon the Bodies $hut up with it, as if they were expo$'d to the pre$$ure of the whole Atmo$phere. That this was not incon- $iderately propounded, we hope Your Lord$hip has gather'd from divers of the things already recited: But yet perhaps it will not be ami$s to $ubjoyn, by way of further confirmation of the $ame truth, the following Experiment, which $hould have accompanied the 20<SUP>th</SUP>, but the Paper where in the one was written chanc'd not to beat hand, when the other was $ent away. <p>We convey'd into the Receiver a new Gla$s Viol, capable of holding about 6 or 7 ounces of Water, into which we had before put 2 or 3 Spoon-fulls of that Li- quor, and $topt it clo$e with a fit Cork. The Pneumatical Ve$$el being empty'd, there appear'd not any change in the in- clo$'d Water, the Air impri$on'd with it, not having the force to blow out the $top- <pb n=215> ple, which event, though it were no other then we expected, was differing from what we de$ir'd. For we would gladly have $een what change would have appear'd in the Water upon the Bottles being $uddenly un$topp'd, in a place where the ambient Body was $o differing from our common Air. Wherefore we did again put in the Viol, but le$s $trongly clo$'d then for- merly, though as $trongly $topt as $eem'd requi$ite on ordinary occa$ions: But when the Air was pump'd out of the Receiver, that within the Viol did quickly, as we expected, find or make it $elf little pa$$a- ges to get out at: as we argu'd, from this, That whereas when the Viol was put in the time before, the Water remain'd all the while perfectly free from bubbles; at this time the bottom of the Gla$s ap- pear'd all cover'd with them, and they, upon the regre$s of the excluded Air into the Receiver, did pre$ently flag and $hrink up. <p>From the$e tryals it $eem'd deducible enough, that whil'$t the Viol continu'd to be well $topt, the included Water did, from the Air, $hut up with it, $u$tain a pre$$ure equal to that of the Atmo$phere; $ince till the Air could get <pb n=216> out of the Gla$s, there appear'd no bub- bles in the Water, notwith$tanding the want of pre$$ure in the ambient Body. <p>But to be $ure to reach the chief end of our Experiment, we made u$e of this o- ther expedient: We cau$'d a convenient quantity of Water to be put, and Her- metically $hut up into a Gla$s Egge, to who$e long Neck (which was purpo$ely made of an unequal thickne$s) was fa- $ten'd to one end of a $tring, who$e o- ther end was ty'd to the Cover of our Receiver, after the manner el$ewhere men- tion'd already: Then the Egge being convey'd into the Pneumatical Ve$$el, and that being evacuated, we did, by turning the bra$s Stopple formerly de- $crib'd among$t the parts of our En- gine, $o $horten the $tring as to break the Gla$s; whereby liberty being given to the Air impri$on'd in the Egge, to pa$s into the capacity of the Receiver, the $ud- den rece$s of the Air made the bubbles in a trice appear $o numerous, and a$cend $o $wiftly in the Water, that their motion look'd like that of a violent $hower of Rain; $ave that the bubbles did not, like the drops of Rain, tend downwards, but upwards, which made me re$emble this <pb n=217> <I>Phænomenon</I> to what I have $een happen in the di$$olution of Seed-Pearl in $ome acid <I>Men$truum,</I> in which, if a good quan- tity of the little Pearls be ca$t whole, they will at fir$t, if the <I>Men$truum</I> be $harp e- nough, be carryed in $warms from the bottom to the top of the Liquor. We will adde, that without $ealing up the Gla$s, this Experiment may be try'd in one of our $malle$t Receivers, for there the ex$uction of the ambient Air may be perform'd $o nimbly, that immediately the bubbles lurking in the Water are al- low'd to di$play them$elves, and a$cend in throngs; in$omuch, as having in $uch a Receiver try'd the Experiment with Wine (as a more $pirituous Liquor) in- $tead of Water, the Red-Wine appear'd all cover'd, with a copious, but vani$hing white Froth, almo$t as if a Ve$$el full of bottl'd drink had been unwarily open'd. <p>IT may not a little conduce to the clear- <MARG><I>Experi- ment</I> 29</MARG> er explication of divers Points in the Doctrine of Meteors, and perhaps of $ome other Phy$iological difficulties, to di$cover what the Air does to the motion of tho$e Steams or Exhalations that a$- <pb n=218> cend into it, namely, Whether they mount upwards by vertue of any $uch <I>po$itive le- vity</I> (as $ome Peripateticks $peak) ac- quir'd together with their Aërial nature, as inables them to pierce through part of the Atmo$phere, and over-come its re- $i$tance. Or el$e, whether the$e $teams being once rai$'d above the Earth by their agitation, have their a$cent and $u$tenta- tion aloft, rather promoted then hindred by the Air: as the inferior parts of that, being thicker and heavier then the $upe- rior, the $teams can more ea$ily continue for a while their agitation upwards then downwards; And afterwards are by the $ame fluidity and thickne$s of the Air, carried to and fro in it, and kept from re- lap$ing to the Earth, as in the Sea water the $aline parts are kept from $ub$iding by tho$e aqueous ones wherewith they are a$$ociated. <p>We hop'd to illu$trate this matter, by ob$erving the motion of the $moke, pro- ceeding from kindled or flaming Bodies in our exhau$ted Receiver. But as we for- merly noted, upon the ex$uction of the Air, the $moking of tho$e Bodies pre- $ently cea$'d. We had thoughts al$o of conveying into our Pneumatical Gla$s a <pb n=219> hot Iron, with $ome Body ea$ie to be di$$ipated into $moke $et upon it, but con- $ider'd, that neither was that way free from inconveniencies; e$pecially this, that the hot Body would make the Impri$on'd Air circulate within the Receiver, and con$equently make it que$tionable whe- ther the a$cent of the $teams would not be due to the new and acquired motion of the Air. <p>Wherefore I bethought my $elf of an- other way to $atisfie in $ome mea$ure my curio$ity, to wit, by means of a certain Liquor, which I call'd to minde that $ome years ago I had (for a de$ign that belongs not to our pre$ent purpo$e) prepar'd; which, I $uppo$e, I $hew'd Your Lord- $hip, and which had the luck to be ta- ken notice of by divers very Ingenious and Famous Men. For this Liquor, though mo$t of its Ingredients be Metals, and all of them ponderous enough, is yet of that nature, that whil$t the Viol where- in it is kept is $topt (how $light a Cover $oever) both the Liquor and the Gla$s are tran$parent; and $o is that upper half of the Gla$s to which the Liquor reaches not. But a$$oon as ever the $topple is ta- ken out, and full acce$s is given to the ex- <pb n=220> ternal Air, both the inward part of the Cork, and the Liquor it $elf, do pre$ent- ly $end upwards, and $catter abroad a fume as thick and white, as if there were a quantity of Alabla$ter-du$t thrown up into the Air: And this $moking of the Liquor la$ts till my unwillingne$s to wa$te it, invites me $top it again; and then the a$cen$ion of the fumes $uddenly cea$es, till the Viol be again un$top'd. <p>This fuming Liquor then I thought would much conduce to the di$covery I de$ir'd to make, $ince it $av'd me the need of conveying any hot Body with it into the Receiver, and would not darken it with fumes before the time. Wherefore having ty'd to the Viol a great weight of Lead, to keep it from being lifted up by the drawing out of the Cork; and having ty'd to the $topple one end of a $tring, of which the other end was made fa$t to the Cover of the Pneumatical Gla$s, the Li- quor was carefully clo$'d up after the wonted manner; then the Air being dili- gently pump'd out, the Viol was un$topt in the empty'd Receiver: and though immediately, npon the drawing out of the Cork, there appear'd to be as it were thrown up $ome white fumes, which <pb n=221> $eem'd to proceed from the Air before impri$on'd in the Viol, and diffu$ing it $elf $uddenly into the capicity of the Receiver. Yet we afterward ob$erv'd, as we expected, That the fumes did not mount and di$per$e them$elves as they u$e to do in the open Air, but that, when by rea$on of the agitation of the Cor- pu$cles of the Liquor, which could not continue their motion in $o narrow a $pace as the Viol afforded them, and were therefore reduc'd to thru$t one another out of it; when, I $ay, by the$e a$$i- $tances the fumes were a$cended to the lip of the Viol, they mounted no higher, but ran down along the out-$ide of the Viol to the bottom of it; and thence along, a long and inclining piece of Lead, on which the Viol re$ted, like a little Stream (not very much bigger then a Swans Quill) who$e nature it $eemd to e- mulate $o well, that it quitted not the Viol till it was come to the bottom of it, and then for$ook it in $uch a manner as a $tream of Water of the $ame bigne$s would have done. And this $tream la$ted a pretty while, and would probably have la$ted longer, but that being loath to wa$te my Liquor, I let in at the Stop-cock a <pb n=222> pretty deal of the external Air; notwith- $tanding which, finding after a while the $tream did run afre$h; though, as it $eem'd, not altogether $o copious as before: I let as much more Air, as would, come in, and found ($omewhat to my wonder) that though the $tream formerly mention'd di$-appear'd, yet there appear'd not any white fumes to ari$e, either from the Cork, or out of the Viol it $elf, no not when the Cover was remov'd from the Recei- ver; though not onely after a while there a$cended white Fumes from the Receiver: but having forthwith taken out the Viol into the open Air, it emitted white ex- halations as before; and having pre$ently after un$top'd it in an open Window, we found both it and the Cork immediatly to $end forth a yet much more plentiful $moak. Though it be now divers years $ince this Numerical Liquor was prepa- red, after the manner mention'd either by <I>Carneiades</I> or <I>Eleutherius</I> (for I do not well remember which) in tho$e Dialogues concerning Heat and Flame that have a- bove been mention'd. <p>More Circum$tances concerning the$e Fumes we might have ob$erv'd, had we not been deterr'd by an Indi$po$ition in <pb n=223> point of health, from having much to do with $teams of $o dangerous a nature, as by that of the Ingredients of this Liquor the$e $eem likely to be of. <p>The Reflections that may be made up- on this Experiment, we have not now the lea$ure to pro$ecute, and therefore $hall content our $elves to recommend the $e- veral Circum$tances of it to Your Lord- $hips $erious con$ideration; and to take notice <I>(en pa$$ant)</I> that $teams in an am- bient Body, or a medium thinner then them$elves, may both tend downwards, and otherwi$e emulate the nature of a Liquor; which I therefore point at, that it may appear the le$s $trange, if we $ome- times $peak of the Atmo$phere as of a kinde of Liquor, in compari$on of that more thin and $ubtle Cele$tial Matter that $urrounds it. <p>And though it might perchance $uf- fice to have on this occa$ion intima- ted thus much; yet, le$t this way of $peaking of the Atmo$phere $hould be thought too bold and extra- vagant, I am content to borrow an Experiment of the Di$cour$e former- <pb n=224> ly mention'd (touching fluidity and firm- ne$s) and $ubjoyn it here with alterations $uitable to the contrivance of our Engine; and this the rather, becau$e I hope it may conduce to the di$covery of the nature of the Atmo$phere: for which rea$on it might have been annext to what has been noted either upon the fir$t, or eighteenth Experiment, but that when they were written and $ent away, it came not into my minde. The Experiment then as we try'd in our Engine, was as follows. <p>WE took one of the $mall Receivers, <MARG><I>Experi- ment</I> 30.</MARG> often mention'd already, and into it we convey'd a piece of well lighted Match; and letting it remain there till it had fill'd the Receiver with $moak, we took it out and ha$tily clo$'d again the Receiver, that the $moak might not get away. Then $taying awhile to let the$e fumes lei$urely $ub$ide, we found, as we expected, that after $ome time they $etled them$elves in the lower half of the Receiver, in a dark- i$h Body, leaving the upper half of the Receiver tran$parent, and as to $ight, full of nought but clear Air. Now to mani- fe$t that this $moak thus $etled emulated <pb n=225> a Liquor, we inclin'd the Engine that con- tain'd it, $ometimes to one $ide, and $ome- times to the other; and ob$erv'd the $moak to keep its $urface almo$t Hori- zontal, notwith$tanding the $tooping of the Ve$$el that held it, as Water or an- other Liquor would in the like ca$e have done. And if by a quicker rocking of the Engine the $moke were more $wiftly $ha- ken, it would, like Water, either Vibrate to and fro from one $ide to the other of the Gla$s, or el$e have its $urface manife$t- ly curll'd with Waves, but pre$erve its $elf in an intire and di$tinct Body from the incumbent Air; and being permitted to re$t awhile, would $oon recover its for- mer $mooth and level <I>$uperficies:</I> If al$o the Key were turn'd and the Valve un- $topp'd, $o that there was a free, though but a narrow pa$$age open'd betwixt the external Air and the cavity of the Recei- ver, then would $ome of this $moak fall down, as it were, in a $tream into the $ub- jacent Cylinder, and a proportionate quantity of the outward Air, would ma- nife$tly a$cend through it into the incum- bent Air, much after the $ame manner as if you invert a Viol with a long Neck, and well fill'd with Red-Wine, into a Gla$s <pb n=226> full of fair water, you $hall $ee the Water and Wine by degrees mingle with one an- other; the one falling downe as it were in little colour'd $treames, and the other a$- cending into its room in the like curled $treames, $ometimes preceded by round parcels of water, which, by rea$on of their tran$parency, looke almo$t like bubbles. The other circum$tances of this Experi- ment, belonging not all of them to our pre$ent purpo$e, we $hall content our $elves with taking notice of one which $eemes the mo$t important, and may illu- $trate and confirme $ome things former- ly delivered. And it was, That if, when the <I>$uperficies</I> of our Smoke lay $mooth and horizontal, a hot iron were held near the our $ide of the Receiver, the Neigh- bouring part of the included fumes (for the re$t did not very much alter their for- mer <I>$uperficies</I>) being rarified by the heat, would readily a$cend in a large Pillar of $moke to the very top of the Receiver, yet without $eeming to loo$e a di$tinct <I>$uperficies,</I> or to be confounded with Air; below which, upon the rece$s of the ad- ventitious heat that by agitating it im- pell'd it upward, it would againe $ub- $ide. <pb n=227> <p>All which being added to the late Ex- periment of the $moking Liquor, and to what may be from that which has been el$ewhere $ayd, gather'd to the $ame pur- po$e, will, I hope, keep it at lea$t from ap- pearing ab$ur'd: If $ince we $ee that there is $o great an inequality in the den$ity and weight of Liquors, that water is neere 14 times thinner or lighter than Quick-$ilver of the $ame bulk, and well dephlegm'd; Spirit of Wine yet much lighter than wa- ter; we venter to $peak $ometimes of the Atmo$phere, as if it were a peculiar kind of thin and halituous Liquor (if I may $o call it) much lighter than Spirit of Wine. <p>To the$e things I know not whether it will be requi$ite to add, that as we late- ly took notice of con$picuous waves that appear'd upon the <I>$uperficies</I> of our agi- tated $moke. So $ome $uch thing may not ab$urdly be conjectur'd to happen on the <I>$uperficies</I> of the Atmo$phere, by tho$e $trange ruggedne$$es that ap- peare (e$pecially in the Spring and Fall, when exhalations and vapours are wont to a$cend mo$t plentifully) upon the Limb or Edge of the Ri$ing and Setting Sun. I $peake thus diffidently upon this occa$ion becau$e I know that by the Fluctuation or <pb n=228> Boyling of the Sun's own <I>$uperficies</I> di- ver$e eminent Mathematicians have plau- $ibly enough (but how truly I leave your Lord$hip to Judge) endeavour'd to give an Account of it. But if we will joine with tho$e that have a$crib'd of late this <I>Phænomenon</I> to the Refraction the Sun- Beames fuffer in our vapid Air; we may, as hath been intimated, promote their Do- ctrin by deducing from it, that probably the $urface Atmo$phere is oftentimes (if not alwayes) exceedingly curl'd or wav'd. And certainly it is $omewhat wonderfull as well as very plea$ant to behold, how, to him that looks upon the $etting Sun through a long & excellent Tele$cope, there will not only appeare $trange ine- qualities in the edge of it (in$omuch that I have often $een it more indented than a Saw) but tho$e inequalities will vani$h in one place and pre$ently appeare in ano- ther, and $eem perfectly to move like waves $ucceeding and de$troying one an- other; $ave that their Motion oftentimes $eemes to be quicke$t as if in that va$t $ea they were carried on by a current, or at lea$t by a tide. And this (as we el$e where note) appear's to the eye not on- ly when it looks directly through the te- <pb n=229> le$cope upon the $unne; but al$o when a large and well defin'd image of the $unne is by the $ame tele$cope brought into a roome and ca$t upon a $heet of white pa- per. But to in$i$t on this were to digre$s: and therefore I will proceed to experi- ments of another kind. <p>IT has been admir'd by very ingenious <MARG><I>Experi- ment</I> 31,</MARG> Men, that if the exqui$itly poli$h'd $urfaces of two flat peeces of marble be $o congruous to each other that from their mutuall application there will re$ult an immediate contact, they will $tick $o fa$t together, that he that lifts up the upper- mo$t, $hall, if the undermo$t be not ex- ceeding heavy, lift up that too, and $u$- taine it aloft in the free aire. A proba- ble cau$e of this $o clo$e adhe$ion we have el$ewhere endeavour'd to deduce from the unequall pre$$ure of the Air upon the un- dermo$t $tone; For the lower <I>$uperficies</I> of that $tone being freely expos'd to the Air is pre$$'d upon by it, whereas the up- permo$t $urface, being contiguous to the $uperiour $tone, is thereby defended from the pre$$ure of the Air which con$equent- ly pre$$ing the lower $tone again$t the up- <pb n=230> per, hinders it from falling, as we have el$ewhere more fully declar'd. Upon the$e grounds we conjectur'd that in ca$e we could procure two marbles exactly ground to one another; and in ca$e we could al$o $ufficiently evacuate our Re- ceiver, the lower $tone would, for want of the wonted and $u$taining pre$$ure of the Air, fall from the upper. But the further tryal of this Experiment we mu$t, unle$s your Lord$hip think it worth Your making at <I>Paris,</I> put off till a fitter opportunity. For where we now are, we cannot procure marbles $o exactly ground, that they will $u$taine one another in the Air, above a minute or two, which is a much $horter time than the emptying of our Receiver requires. We did indeed try to make our marbles $tick clo$e to- gether by moi$tening their polli$hed $ur- faces with rectifi'd $pirit of Wine, in re- gard that Liquor by its $udden avolation from marble, if powr'd thereon, without leaving it moi$t or le$s $mooth, $eem'd unable to $u$taine them together after the manner of a glutinous body, and yet $eem'd $ufficient to exclude and keep out the Air. But this we try'd to little pur- po$e, for having convey'd into the Recei- <pb n=231> ver two black $quare marbles (the one of two inches and a third in length or breadth, and $omewhat more than halfe an inch in thickne$s: The other of the $ame extent, but not much above halfe $o thick) fa$ten'd together by the interven- tion of pure Spirit of Wine; and having $u$pended the thicker by a $tring from the cover, we found not that the ex$uction of the ambient Air would $eparate them, though a weight amounting to four oun- ces were fa$ten'd to the lowermo$t mar- ble to facilitate it's falling off. <p>I would gladly have the Experiment try'd with marble $o well polli$h't as to need no Liquor what$oever to make them cohere, and in a Ve$$el out of which the Air may be more perfectly drawn than it was out of ours. But in the mean time though we will not determin whether the Spirit of wine did contribute to the $trong cohe$ion of the$e $tones, otherwi$e than by keeping ev'n the $ubtl'$t parts of the Air from getting in between them, yet it $eemed that the not falling downe of the lowermo$t marble might without impro- bability be a$crib'd to the pre$$ure of the Air remaining in the Receiver; which as we formerly noted having been able <pb n=232> to keep a Cylinder of water of above a Foot in height from falling to the bot- tom of the Tube, may well enough be $uppo$'d capable of keeping $o broad a flat Marble from de$cending. And though this may $eem a $trange proof of the $trength of the $pring of Air, ev'n when rarified, yet it will $carce $eem incredible to him that has ob$erv'd how exceeding $trong a cohe$ion may be made betwixt broad Bodies, one- ly by their immediate touching one ano- ther. A notable in$tance of which, I have met with in this $hort Narrative of <MARG><I>P. Nic. Zucchius opal Schot: part</I> 1. <*></MARG> the Learned <I>Zucchius. Fuveni</I> ($ays he) <I>lacertorum $uorum robur: jactanti propo- $ita $emel e$t lamina ærea, per an$am in medio extantem apprehen$am elevanda è tabula marmorea, cui optime congruebat: qui primo tanquam rem ludicr am puero committendam contemp$it: tum in$tanti- bus amicis manum utrámque admovens, cum luctatus diu hærentem non removi$$et, excu$avit impotentiam, objecta perigrini & potenti$simi glutinis interpo$itione, quo forti$sime copulante nequiret divelli; do- nec vidit ab alio per tabulam facilimè lami- nam deduci, & ad extrema product am, & actam in tran$ver$um inàe deportari.</I> But that we may learn from our own Engine, <pb n=233> that two Bodies, though they touch each other but in a $mall part of their $urfaces, may be made to cohere very $trongly, onely by this, That the Air pre$$es much more forcibly upon the inferior $uperfi- cies of the lowermo$t Body, then upon the upper $urface of the $ame: We will hereunto annex the following Experi- ment, though out of the order wherein they were made. <MARG><I>Experi- ment</I> 32.</MARG> <p>I remember I have, in a Di$cour$e con- cerning Fluidity and Firmne$s, made mention of my having, by the ex$uction of the Air out of a Gla$s Ve$$el, made that Ve$$el take up, or $uck up (to $peak in the common Language) a Body weighing divers Ounces; but our Engine affording us the opportunity of making con$ider- abler Experiments of that kinde, We thought fit to make a further tryal of the force of the Atmo$phere's pre$$ure up- wards, after the following manner. <p>The Receiver having been exqui$itely clo$'d, as we have often taught already, and the Air being in a good mea$ure drawn out of it, it was remov'd from off the Pump: and to the lower Branch of the <pb n=234> Stop-cock, there was $peedily apply'd a tapering Valve of bra$s, $uch as is de$crib'd in the 9<SUP>th</SUP> fig: made fit to go with its nar- rower end into the cavity of the branch, and to fill the orifice of that cavity with its broader part. And that the Air might not get in at the litle intervals, left here and there between the convex $urface of the $topple and the internall edge of the branch, tho$e intervals were $top't with a little Diachylon. And to the doore, or, (if you plea$e) that part of the Valve which was to move to and fro, and in this Experiment hung perpendicular to the Horizon, there was, at a button of bra$s belonging to the Valve fa$ten'd a broad $cale wherein weights were to be put. This done the key of the Stop-cock was turn'd, and the externall Air beating like a forcible $treame upon the Valve to get in there, it did $uddenly both $hut the Valve and keep it $hut $o $trongly, that we had time to ca$t in diver$e weights one after another into the Scale; till at length the weight overpowering the pre$- $ure of the Atmo$phere, drew downe the Valve by the $tringes that ty'd the Scale to it, and gave liberty to the outward Air to ru$h into the Receiver. Though a- <pb n=235> nother time, when the Valve had but lit- tle weight hanging at it, being, by I know not what accident, drawn down beneath its former place, it was by the impetuous current of the outward Air $uddenly im- pell'd up into it again, and kept there. But in the former Experiment it is re- markable, That though the Receiver were not well exhau$ted, and though it leak'd whil'$t the re$t of the Experiment was in pro$ecution, and though the Valve whereon the Cylinder of the Atmo$phere could pre$s, were not above an Inch and a half in Diameter, yet the weight kept up by $uction, or rather $upported by the Air, namely the Valve, the Seal and what was ca$t into it, being $ent to be weigh'd, amounted to about ten of our common Pounds, con$i$ting of $ixteen Ounces apiece: So that we doubted not but that, had the Experiment been made with favorable Circum$tances, the Air endeavoring to pre$s in at the Orifice of the Stop-cock, would have kept a very much greater weight from falling out of it; I $ay the Air, becau$e we found, by tryal purpo$ely made, that neither the imperfect contact of the Valve and the Stop-cock, nor the Diachylon that was <pb n=236> employ'd to fill up the little Crannies left betwixt them, were con$iderable in this Experiment; by which may among other things appear, that I did not without cau$e in the above-nam'd Di$cour$e touch- ing Fluidity and Firmne$s, a$cribe a great force, ev'n to $uch Pillars of Air as may be $uppo$'d to begin at the top of the Atmo$phere, and recoyling from the ground to terminate on the Bodies on which they pre$s: $ince in the pre$ent Ex- periment $uch a weight was $upported by $o $lender a Cylinder of Air, rebounding from the Earth to the Valve whereon it did bear. <p>BUt in regard we have not yet been <MARG><I>Experi- ment</I> 33.</MARG> able to empty $o great a Ve$$el as our Receiver, $o well as we can the Cylinder it $elf; our Pump alone may afford us a nobler in$tance of the fotce of the Air we live in, in$omuch, that by help of this part of our Engine, we may give a pretty near ghe$s at the $trength of the Atmo- $phere, computed as a weight. And the way may be this; Fir$t, the Sucker be- ing brought to move ea$ily up and down the Cylinder, is to be impell'd to the top <pb n=237> of it: Then the Receiver mu$t be taken off from the Pump, that the upper Ori- fice of the Cylinder remaining open, the Air may freely $ucceed the Sucker, and therefore readily yield to its motion downward. This done, there mu$t be fa$ten'd to one of the Iron Teeth of the Sucker, $uch a weight as may ju$t $uffice to draw it to the bottom of the Cylinder. And having thus examin'd what weight is nece$$ary to draw down the Sucker, when the Atmo$phere makes no other then the ordinary re$i$tance of the Air again$t its de$cent; the Sucker mu$t be again forc'd to the top of the Cylinder, who$e upper Orifice mu$t now be exactly clo$ed; and then (the fir$t weight remaining) we ea$i- ly may, by hanging a Scale to the above- mention'd Iron (that makes part of the Sucker) ca$t in known weights $o long, till in $pight of the reluctancy of the At- mo$phere the Sucker be drawn down. For to the$e weights in the Scale, that of the Scale it $elf being added, the $um will give us the weight of a Column of Air, equal in Diameter to the Sucker, or to the ca- vity of the Cylinder; and in length to the heighth of the Atmo$phere. <p>According to this method we did, $ince <pb n=238> the writing of the la$t Experiment, at- tempt to mea$ure the pre$$ure of the At- mo$phere, but found it more difficult then we expected, to perform it with any ac- curatene$s; for though by the help of the <I>Manubrium</I> the Sucker moved up and down with $o much ea$e, that one would have thought that both its convex $urface, and the concave one of the Cylinder were exqui$itely $mooth, & as it were $lippery; yet when the Sucker came to be moved onely with a dead weight or pre$$ure (that was not (like the force of him that pump'd) intended as occa$ion required) we found that the little rufne$$es, or other inequalities, and perhaps too, the unequal pre$$ure of the Leather again$t the cavity of the Cylinder, were able now and then to put a $top to the de$cent or a$cent of the Sucker, though a very little external help would ea$ily $urmount that impedi- ment; and then the Sucker would, for a while, continue its formerly interrupted motion, though that a$$i$tance were with- drawn. But this di$couragement did not deterre us from pro$ecuting our Experi- ment, and endeavoring, by a careful trial, to make it as in$tructive as we could. We found then that a Leaden Weight, <pb n=239> of 28 pounds (each con$i$ting of $ixteen Ounces) being fa$tned to one of the teeth of the Sucker, drew it down $lowly e- nough; when the upper Orifice of the Cylinder was left open, though by the help of Oyl and Water, and by the fre- quent moving the Sucker up and down with the <I>Manubrium,</I> its motion in the Cylinder had been before purpo$ely faci- litated. This done, the upper Orifice of the Cylinder was very carefully and clo$e- ly $topp'd, the Valve being likewi$e $hut with its wonted Stopple well oyl'd, af- ter the Sucker had been again impell'd up to the top of the Cylinder. Then to the precedent twenty eight pound, we added a hundred and twelve pounds more, which forcing down the Sucker, though but lei$urely, we took off the twenty eight pound weight; and being unable to procure ju$t $uch weights as we would have had, we hung on, in$tead of it, one of fourteen pound, but found that, with the re$t, unable to carry down the Sucker. And to $atisfie our $elves, and the Spe- ctators, that it was the re$i$tance of the ambient Air that hinder'd the de$cent of $o great a weight, after that we had try'd that upon un$topping the Valve, and <pb n=240> thereby opening an acce$s to the external Air, the Sucker would be immediately drawn down: After this, I $ay, we made this further Experiment, That having by a Man's $trength forcibly depre$$'d the Sucker to the bottom of the Cylinder, and then fa$tned weights to the above- named Iron that makes part of that Suc- ker, the pre$$ure of the external Air find- ing little or nothing in the cavity of the evacuated Cylinder to re$i$t it, did pre- $ently begin to impell the Sucker, with the weights that clogg'd it, towards the upper part of the Cylinder, till $ome $uch accidental Impediment as we former- ly mention'd, check'd its cour$e; and when that rub, which ea$ily might be, was taken out of the way, it would continue its a$cent to the top, to the no $mall won- der of tho$e By $tanders, that could not comprehend how $uch a weight could a$- cend, as it were, of it $elf; that is, with- out any vi$ible force, or $o much as Su- ction to lift it up. And indeed it is very con$iderable, that though po$$ibly there might remain $ome particles of Air in the Cylinder, after the drawing down of the Sucker; yet the pre$$ure of a Cylinder of the Atmo$phere, $omewhat le$s then <pb n=241> three Inches in Diameter (for, as it was $aid in the de$cription of our Engine, the cavity of the Cylinder was no broader) was able, uncompre$$'d, not only to $u$tain, but even to drive up a weight of an hun- dred and odde pounds: for be$ides the weight of the whole Sucker it $elf, which amounts to $ome pounds, the weights an- nexed to it made up a hundred and three pounds, be$ides an Iron Bar, that by con- jecture weighed two pounds more; and yet all the$e together fall $omewhat $hort of the weight which we lately mention'd, the re$i$tance of the Air to have held $u- $pended in the cavity of the Cylinder. <p>And though (as hath been already ac- knowledg'd) we cannot, peradventure, obtain by the recited means $o exact an account as were to be wi$h'd, of what we would di$cover: Yet, if it $erve us to ground Conjectures more approaching to the Truth, then we have hitherto met with, I hope it will be con$ider'd (which a famous Poet judiciou$ly $ays) <C><I>E$t quoddam prodire tenus, $i non da- tur ultra.</I></C> <p>Peradventure it will not be imperti- <pb n=242> nent to annex to the other Circum$tances that have been already $ee down concern- ing this Experiment, That it was made in Winter, in Weather neither Fro$ty nor Rainy, about the change of the Moon, and at a place who$e latitude is near about 51<SUP>d</SUP> and a half: For perhaps the force or pre$$ure of the Air may vary, according to the Sea$ons of the Year, the tempera- ture of the Weather, the elevation of the Pole, or the pha$es of the Moon; all, or even any of them $eeming capable to al- ter either the heighth or con$i$tence of the incumbent Atmo$phere: And therefore it would not be ami$s if this Experiment were carefully tryd at $everal times and places, with variety of Circum$tances. It might al$o be try'd with Cylinders of $e- veral Diameters, exqui$itely fitted with Suckers, that we might know what pro- portion $everal Pillars of the Atmo$phere bear, to the Weights they are able to $u- $tain or lift up; and con$equently, whe- ther the increa$e or decrement of the re- $i$tance of the ambient Air, can be re- duc'd to any regular proportion to the Diameters of the Suckers: The$e, and divers other $uch things which may be try'd with this Cylinder, might mo$t of <pb n=243> them bemore exactly try'd by the To<*>- cellian Experiment, if we could get Tubes $o accurately blown and drawn, that the Cavity were perfectly Cylindrical. <p>To dwell upon all the $everal Refle- ctions, that a $peculative Wit might make upon this and the foregoing Expe- riment: (I mean the thirty third and thir- ty $econd, would require almo$t a Vo- lume, whereas our occa$ions will $carce allow us time to touch upon three or four of the chief Inferences that $eem de- ducible from them, and therefore we $hall content our $elves to point at tho$e few. <p>And fir$t, as many other <I>Phænomena</I> of our Engine, $o e$pecially, the two lately mention'd Experiments, $eem ve- ry much to call in que$tion the receiv'd Opinion of the Nature or Cau$e of Su- ction. For 'tis true indeed, that when men $uck, they commonly u$e $ome manife$t endeavour by a peculiar motion of their Mouthes, Che$ts, and $ome other con$pi- ring parts, to convey to them the body to be $uckt in. And hence perhaps they have taken occa$ion, to think that in all <pb n=244> Suction there mu$t be $ome Endeavour or motion in the $ucking to attract the $ucked Body. But in our la$t Experi- ment it appeares not at all how the up- per part of the empty'd Cylinder that re- maines movele$s all the while, or any part of it, does at all endeavour to draw to it the depre$$ed Sucker and the an- nex'd weights. And yet tho$e that be- hold the a$cention of the Sucker, without $eriou$ly con$idering the cau$e of it, doe readily conclude it to be ray$'d by $ome- thing that powerfully Sucks or attracts it, though they $ee not what that may be or where it lurks. So that it $eemes not ab$olutely nece$$ary to Suction, that there be in the Body, which is $aid to $uck, an endeavor or motion in order thereun- to, but rather that Suction may be at lea$t for the mo$t part reduc'd to Pul$ion, and its effects a$crib'd to $uch a pre$$ure of the neighboring air upon tho$e Bodies (whther aërial, or of other Natures) that are contiguous to the Body that is $ayd to attract them, as is $tronger than that Sub- $tance which po$$e$$es the cavity of that $ucking Body is able to re$i$t. To ob- ject here, that it was $ome particles of Air remaining in the empty'd Cylin- <pb n=245> der that attracted this weight to obviate a <I>Vacuum,</I> will $carce be $atisfactory; un- le$s it can be cleerly made out by what li- tle hooks, or other grappling In$truments, the internal Air could take hold of the Sucker; how $o litle of it obtain'd the force to lift up $o great a weight; and why al$o, upon the letting in of a litle more Air into one of our evacuated Ve$- $els, the attraction is, in$tead of being $trengthen'd, much weaken'd, though, if there were danger of a <I>Vacuum</I> be- fore, it would remain, notwith$tanding this ingre$s of a little Air. For that $till there remain'd in the capacity of the ex- hau$ted Cylinder $tore of little rooms, or $paces empty or devoid of Air, may appear by the great violence wherewith the air ru$hes in, if any way be open'd to it. And that 'tis not $o much the decrement of the <I>Vacuum</I> within the cavity of the ve$$el that debilitates the attraction, as the $pring of the included air (who$e pre$ence makes the decrement) that does it by re$i$ting the pre$$ure of the external Air, $eems probable, partly from the Di$abi- lity of vacuities, whether greater or le$$er, to re$i$t the pre$$ure of the Air; and part- ly by $ome of the <I>Phænomena</I> of our Ex- <pb n=246> periments, and particularly by this Cir- cum$tance of the three and Thirtieth, that the Sucker was by the pre$$ure of the Ambient Air impell'd upwards, with its weight hanging at it, not only when it was at the bottome of the Cylinder, and con$equently left a great <I>Vacuum</I> in the cavity of it; but when the Sucker had been already impel'd almo$t to the top of the Cylinder, and con$equently, when the <I>Vacuum</I> that remain'd was become very litle in compari$on of that which preceded the beginning of the Sucker's a$cention. <p>In the next place, the$e Experiments may teach us, what to judge of the vul- gar Axiom receiv'd for $o many Ages as an undoubted Truth in the Peripate- tick Schools; That Nature abhorres and flys a <I>Vacuum,</I> and that to $uch a de- gree, that no humane power (to go no higher) is able to make one in the Uni- ver$e; wherein Heaven and Earth would change places, and all its other Bodyes rather act contrary to their own Nature, than $uffer it. For, if by a <I>Vacuum</I> we will under$tand a place perfectly devoid of all corporeal Sub$tance, it may be in- deed then, as we formerly noted be plau- $ibly enough maintain'd, that there is <pb n=247> no $uch thing in the world; but that the generality of the Pleni$ts, (e$pecially till of late yeares $ome of them grew more wary) did not take a <I>Vacuum</I> in $o $trict a Sen$e, may appear by the Experiments formerly, and ev'n to this Day imploy'd by the Deniers of a Vacuum, to prove it impo$$ible that there can be any made. For when they alleadge (for In$tance) that when a man $ucks Water through a long Pipe, that heavy Liquor, contrary to its Nature, a$cends into the Sucker's mouth, only, to fill up that room made by the Dilatation of his Bre$t and Lungs, which otherwi$e will in part be empty. And when they tell us, that the rea$on why if a long Pipe exactly clos'd at one end be fill'd top-ful of Water, and then inverted, no Liquor will fall out of the open Orifice; Or, to u$e a more familiar Example, when they teach, that the cau$e why in a Gardiner's watering Pot $hap'd conically, or like a Sugar-Loaf fill'd with Water, no Liquor fals down through the numerous holes at the bottome, whil$t the Gardiner keeps his Thumb upon the Orifice of the litle hole at the top, and no longer, mu$t be that it in the ca$e propo$ed the Water <pb n=248> $hould de$cend, the Air being unable to $ucceed it, there would be left at the up- per and de$erted part of the Ve$$el a <I>Va- cuum,</I> that would be avoided if the hole at the top were open'd. When (I $ay) they alleadge $uch Experiments, the Tendency of them $eems plainly to im- port, that they mean, by a <I>Vacuum,</I> any $pace here below that is not fill'd with a vi$ible body, or at lea$t with Air; though it be not quite devoy'd of all Body what- $oever. For why $hould Nature, out of her dete$tation of a <I>Vacuum,</I> make Bo- dies act contrary to their own Tendency, that a place may be fill'd with Air, if its being $o were not nece$$ary to the avoi- ding of a <I>Vacuum.</I> <p>Taking then a <I>Vacuum</I> in this vulgar and obvious $ence, the common opinion about it $eems lyable to $everal Exce- ptions, whereof $ome of the chief are $ugge$ted to us by our Engine. <p>It will not ea$ily then be intelligibly made out, how hatred or aver$ation, which is a pa$$ion of the Soule, can either for a <I>Vacuum,</I> or any other object, be $up- pos'd to be in Water, or $uch like inani- mate Body, which cannot be pre$um'd to know when a <I>Vacuum</I> would en$ue; if <pb n=249> they did not be$tirre them$elves to pre- vent it, nor to be $o generous as to act contrary to what is mo$t conducive to their own particular pre$ervation for the publique good of the Univer$e. As much then of intelligible and probable Truth, as is contain'd in this Metaphoricall Ex- pre$$ion, $eems to amount but to this; That by the Wi$e Author of Nature (who is ju$tly $ayd to have made all things in number, weight, and mea$ure,) the Univer$e, and the parts of it, are $o contriv'd, that it is as hard to make a <I>Va- cuum</I> in it, as if they $tudiou$ly con$pir'd to prevent it. And how far this it $elfe may be granted, de$erves to be further con$ider'd. <p>For in the next place, our Experiments $eem to teach, that the $uppo$ed Aver$a- tion of Nature to a <I>Vacuum</I> is but acci- dental, or in con$equence partly of the Weight and Fluidity, or, at lea$t, Fluxi- lity of the Bodies here below; and partly, and perhaps principally, of the Spring of the air, who$e re$tle$s endeavor to expand it $elfe every way, makes it either ru<*>h in it $elfe, or compel the interpos'd bo- dys into all $paces, where it finds no grea- ter re$i$tance than it can $urmount. And <pb n=250> that in tho$e motions which are made <I>ob- fugamVacui</I> (as the common phra$e is) Bo- dys act without $uch genero$ity & Con- $ideration, as is wont to be a$crib'd to them, is apparent enough in our 32<SUP>d</SUP> Ex- periment, where the torrent of Air, that $eem'd to $trive to get into the Empty'd Receiver, did plainly prevent its own De$igne, by $o impelling the Value, as to make it $hut the only Orifice the Air was to get in at. And if afterwards ei- ther Nature, or the internal Air, had a de- $igne the external Air $hould be attra- cted, they $eem'd to pro$ecute very un- wi$ely by continuing to $uck the Valve $o $trongly, when they found that by that Sucction the Valve it $elfe could not be drawn in: Whereas by forbearing to $uck, the Valve would by it's own weight have fall'n down, and $uffer'd the exclu- ded Air to returne freely, and to fill again the exhau$ted Ve$$el. <p>And this minds me to take notice of another deficiency, pointed at by our Ex- periments in the common Doctrine of tho$e Pleni$ts we rea$on with; for many of tho$e unu$ual motions in Bodies, that are $ayd to be made to e$cape a <I>Vacuum,</I> $eem rather made to fill it. For why, <pb n=251> to in$tance in our newly mention'd Ex- periment, a$$oon as the Valve was de- pre$s'd by the weight we hung at it, $hould the Air $o impetuou$ly and copi- ou$ly ru$h into the cavity of the Receiver; if there were before no vacant room there to receive it? and if there were, then all the while the Valve kept out the Air, tho$e litle $paces in the Receiver, which the corpu$cles of that Air afterwards fill'd, may be concluded to have remain'd em- pty. So that the $eeming violence, imploy'd by Nature on the occa$ion of the evacuating of the Ve$$el, $eems to have come too late to hinder the making of Vacuities in the Receiver, and only to have, a$$oon as we permitted, fill'd up with Air tho$e that were already made. <p>And as for the Care of the Publique Good of the Univer$e a$crib'd to dead and $tupid Bodies, wee $hall only de- mand, why in our 19<SUP>th</SUP> Experiment, upon the Ex$uction of the ambient Air, the Water de$erted the upper half of the Gla$s-Tube; and did not a$cend to fill it up, till the external Air was let in upon it: whereas by its ea$y and $udden regai- ning that upper part of the Tube, it <pb n=252> appear'd both that there was there much $pace devoid of Air, and that the Water might with $mall or no re$i$tance have a$cended into it, if it could have done $o without the impul$ion of the readmitted Air; which, it $eems, was nece$$ary to mind the Water of its formerly neglected Duty to the Univer$e. <p>Nay, for ought appeares, ev'n when the excluded Air, a$$oon as 'twas per- mitted, ru$ht violently into our exhau- $ted Receiver, that flowing in of the Air proceeded rather from the deter- minate Force of the Spring of the neighbouring Air, then from any endea- vour to fill up, much le$s to prevent va- cuity's. For though when as much Air as will, is gotten into our Receiver our pre- $ent Opponents take it for granted that it is full of Air; yet if it be remembred that when we made our 17<SUP>th</SUP> Experiment we crouded in more Air to our Receiver than it u$ually holds; and if we al$o con- $ider (which is much more) the Air of the $ame con$i$tence with that in our Receiver may in wind guns, as is known, and as we have try'd, be compre$$ed at lea$t into halfe its wonted room (I $ay at lea$t, becau$e $ome affirme, that the Air <pb n=253> may be thru$t into an 8<SUP>th</SUP>, or a yet $maller part of its ordinary extent) it $eems ne- ce$$ary to admit either a notion of conden- $ation & rarefaction that is not intelligi- ble, or that in the capacity of our Recei- ver when pre$um'd to be full of Air, there yet remain'd as much of $pace as was ta- ken up by all the aërial corpu$cles unpo$- $e$$ed by the Air. Which $eemes plainly, to infer that the Air that ru$h'd into our empty'd ve$$el did not doe it preci$ely to fill up the Vacuities of it, $ince it left $o many unfill'd, but rather was thru$t in by the pre$$ure of the contiguous Air; which as it could not, but be always ready to ex- pand it $elfe, where it found lea$t re$i- $tance, $o was it unable to fill the Recei- ver any more, then until the Air within was reduc'd to the $ame mea$ure of Com- pactne$s with that without. <p>We may al$o from our two already of- ten mention'd Experiments further de- duce, that, ($ince Natures hatred of a <I>Vacuum</I> is but Metaphorical and Ac- cidental, being but a con$equence or re- $ult of the pre$$ure of the Air and of the Gravity, and partly al$o of the Fluxility of $ome other bodies) The power $hee makes u$e of to hinder a Vacuum, is not <pb n=254> (as we have el$e-where al$o noted) any $uch boundle$s thing as men have been pleas'd to imagine. And the rea$on, why in the former Experiments, mentioned in favour of the Pleni$ts, Bodies $eem to forget their own Natures to $hun a <I>Va- cuum,</I> $eems to be but this; That in the alleadged ca$es the weight of that Wa- ter that was either kept from falling or impell'd up, was not great enough to $urmount the pre$$ure of the contiguous Air; which, if it had been, the Water would have $ub$ided, though no Air could have $ucceeded. For not to repeat that Experiment of Mon$ieur <I>Pa$chal</I> (for- merly mention'd to have been try'd in a Gla$s exceeding 32 Foot) wherein the inverted Pipe being long enough to con- tain a competent weight of Water, that Liquor freely ran out at the lower Orifice: Not to mention this (I $ay) we $aw in our nineteenth Experiment, that when the pre$$ure of the ambient Air was $uffi- ciently weaken'd, the Water would fall out apace at the Orifice even of a $hort Pipe, though the Air could not $ucceed into the room de$erted by it. And it were not ami$s if tryal were made on the tops of very high Mountains, to di$cover with <pb n=255> what ea$e a <I>Vacuum</I> could be made near the confines of the Atmo$phere, where the Air is probably but light in compari- $on of what it is here below. But our pre$ent (three and thirtieth) Experiment $eems to manife$t, not onely that the power, exerci$'d by Nature, to $hun or re- pleni$h a <I>Vacuum,</I> is limited, but that it may be determin'd even to Pounds and Ounces: In$omuch that we might $ay, $uch a weight Nature will $u$tain or will lift up to re$i$t a <I>Vacuum</I> in our Engine; but if an Ounce more be added to that weight, it will $urmount Her $o much magnifi'd dete$tation of Vacuities. And thus, My Lord, our Experiments may not onely an$wer tho$e of the Pleni$ts, but enable us to retort their Arguments again$t them$elves: $ince, if that be true which they alleadge, that, when Water falls not down according to its nature, in a Body wherein no Air can $ucceed to fill up the place it mu$t leave, the $u$pen$i- on of the Liquor is made <I>Ne detur Vacu- um,</I> (as they $peak) it will follow, that if the Water can be brought to $ub$ide in $uch a ca$e, that de$erted $pace may be deem'd empty, according to their own Doctrine; e$pecially, $ince Nature (as <pb n=256> they would per$wade us) be$tirs her $elf $o mightily to keep it from being de- $erted. <p>I hope I $hall not need to reminde Your Lord$hip, that I have all this while been $peaking of a <I>Vacuum,</I> not in the $trict and Philo$ophical $en$e, but in that more obvious and familiar one that has been formerly declar'd. <p>And therefore I $hall now proceed to ob$erve in the la$t place, that our 33<SUP>d</SUP> Ex- periment affords us a notable proof of the unheeded $trength of that pre$$ure which is $u$tain'd by the Corpu$cles of what we call the free Air, and pre$ume to be un- compre$$'d. For, as fluid and yielding a Body as it is, our Experiment teaches us, That ev'n in our Climate, and without any other compre$$ion then what is (at lea$t here below) Natural, or (to $peak more properly) ordinary to it, it bears $o $trongly upon the Bodies whereunto it is contiguous, that a Cylinder of this free Air, not exceeding three Inches in Dia- meter is able to rai$e and carry up a weight, amounting to between $ixteen and $eventeen hundred Ounces. I $aid, <pb n=257> even in our Climate, becau$e that is tem- <MARG><I>Aere $rig<*>- do exi$tcate tardius mo- <*>entur Au- tomat a quã acre ca<*>ida, adco qui- dem ut Au- tomaton quod Delgæ in Nova Zembla a- gentes in æ- dibus $u<*>s collocave- runt, omal- no à motis ce$$ave<*>it <*>t$i m<*> malus toa- dus ei addidi$$ent quam antea ferre $olebat.</I> Varenius Geo: Genevat <*>. 111. Propo: 7. pag. 648.</MARG> perate enough; and as far as my ob$er- vations a$$i$t me to conjecture, the Air in many other more Northern Countries may be much thicker, and able to $upport a greater weight: which is not to be doubted of, if there be no mi$take in what is Recorded concerning the <I>Hollan- ders,</I> that were forc'd by the Ice to Win- ter in <I>Nova Zembla,</I> namely, That they found there $o conden$'d an Air, that they could not make their Clock goe, ev'n by a very great addition to the weights that were wont to move it. <p>I $uppo$e Your Lord$hip will readily take notice, that I might very ea$ily have di$cour$ed much more fully and accuratly then I have done, again$t the common o- pinion touching Suction, and touching na- tures hatred of a <I>Vacuum.</I> But I was willing to keep my $elf to tho$e con$iderations touching the$e matters, that might be ve- rifi'd by our Engine it $elf, e$pecially, $ince, as I $aid at fir$t, it would take up too much time to in$i$t particularly upon all the Re- flections that may be made even upon our two la$t Experiments. And therefore, <pb n=258> pa$$ing to the next, I $hall leave it to your Lord$hip to con$ider how far the$e tryals of ours will either confirm or disfavor the new Doctrine of $everal eminent Na- turali$ts, who teach, That in all motion there is nece$$arily a Circle of Bodies, as they $peak, moving together; and whe- ther the Circles in $uch motion be an Ac- cidental or Con$equential thing or no. <p>TIs a known thing to tho$e that are con- <MARG><I>Experi- ment</I> 34.</MARG> ver$ant in the Hydro$taticks, That two Bodies which in the Air are of equal weight, but of unequal bulk, as Gold, for in$tance and Iron, being afterwards weighed in Water, will lo$e their <I>Æqui- librium</I> upon the change of the ambient Body, $o that the Gold will $ink lower then the Iron; which, by rea$on of its greater bulk, has more Water to lift or di$place, that it may $ink. By Analogy to this Experiment, it $eem'd probable, that if two weights did in our Engine ballance each other, when the Gla$s was full of Air; upon the ex$uction of a great part of that Air, $o notable a change in the con$i$tence of the ambient Body, <pb n=259> would make them lo$e their <I>Æquili- brium.</I> <p>But being de$irous at the $ame time to make a tryal, for a certain De$ign that needs not here be mention'd, we took for one of our weights a dry Bladder, $trongly tyed at the Neck, and about half fill'd with Air (that being a weight both $light, and that would expand it $elf in the evacuated Gla$s) and fa$tning that to one part of our formerly menti- on'd exact ballance (which turns with the 32<SUP>d</SUP> part of a Grain) we put a Metalline counterpoi$e into the oppo$ite Scale; and $o the two weights being brought to an <I>Æquilibrium,</I> the ballance was convey'd into the Receiver, and $u$pended from the Cover of it. <p>But before we proceed further, we mu$t note, That pre$ently after the laying on of the Cover, the Bladder appear'd to preponderate, whereupon the Scales being taken out, and reduc'd very near to an <I>Æ- quilibrium,</I> yet $o, that a little advantage remain'd on that $ide to which the Metal- line weight belong'd; they were again let down into the Receiver, which was pre- $ently made fa$t with Plai$ter, and a hot Iron: Soon after which, before the Pump <pb n=260> was employ'd, the Bladder $eem'd again a little to preponderate. Afterwards the Air in the Gla$s being begun to be drawn out, the Biadder began (according to the formerly mention'd Ob$ervations) to expand it $elf, and manife$tly to out- weigh the oppo$ite weight, drawing down the Scale to which it was fa$tned very much beneath the other, e$pecially when the Air had $well'd it to its full ex- tent. <p>This done, we very lei$urely let in the external Air; and ob$erv'd, that upon the flagging of the Bladder, the Scale whereto it was fa$tned, not onely by de- grees return'd to an <I>Æquilibrium</I> with the other, but at length was a little out- weighed by it. <p>But becau$e we $u$pected there might have interven'd $ome unheeded Circum$tance in this la$t part of the Ex- periment, we would not pre$ently take out the Scales, nor meddle with the Co- ver, but leaving things as they were, we perceiv'd, that after a little while the Bladder began again to preponderate, and by degrees to $ink lower and lower for divers hours; wherefore, leaving the Ve$$el clo$'d up all night, we repair'd to it <pb n=261> next Morning, and found the Bladder fallen yet lower. As if the very $ub$tance of it, had imbibed $ome of the moi$ture wherewith the Air (the Sea$on being ve- ry rainy) did then abound: As Lute- $trings, which are made likewi$e of the Membranous parts of Guts, $trongly wreath'd, are known to $well $o much, oftentimes as to break in rainy and wet weather. Which conjecture is the more to beregarded, becau$e congruou$ly unto it one of the company having a little warm'd the Bladder, found it then lighter then the oppo$ite weight. But this mu$t be look'd upon as a bare conjecture, till we can gain time to make further tryals about it. In the mean while we $hall adde, that without removing the Scales or the Co- ver of the Receiver, we again cau$'d the Air to be drawn out (the weather conti- ing very moi$t) but found not any manife$t alteration in the ballance; whether be- cau$e the <I>Æquilibrium</I> was too far lo$t to let a $mall change appear, we determine not. <p>But to make the Experiment with a Body le$s apt to be altered by the tempe- rature of the Air, then was the Bladder; we brought the Scales again to an <I>Æqui-</I> <pb n=262> <I>librium</I> with two weights, whereof the one was of Lead, the other of Cork. And having evacuated the Receiver, we ob$er- ved, that both upon the ex$uction, and after the return of the Air, the Cork did manife$tly preponderate, and much more a while after the Air had been let in again, then whil$t it was kept out. Wherefore, in the room of the Cork, we $ub$tituted a piece of Char-coal, as le$s likely to im- bibe any moi$ture from the Air, but the event proved much the $ame with that newly related: So that this Experiment $eems more liable to Ca$ualties then any, excepting one we have made in our En- gine. And as it is difficult to prevent them, $o it $eems not very ea$ie to di$- cover the cau$es of them, whereof we $hall therefore at pre$ent forbear mention- ing our Conjectures. <p>SOme Learned Mathematicians have of <MARG><I>Experi- ment</I> 35.</MARG> late ingenioù$ly endeavored to reduce Filters to <I>Siphons;</I> but $till the true cau$e of the a$cen$ion of Water, and other Li- quors, both in <I>Siphons</I> and in Filtration, needing (for ought we have yet found) a clearer Di$covery and Explication, we <pb n=263> were de$irous to try whether or no the pre$$ure of the Air might rea$onably be $uppo$'d to have either the principal, or at lea$t a con$iderable Intere$t in the rai$ing of tho$e Liquors. But becau$e we found that we could not yet $o evacuate our Re- ceiver, but that the remaining Air, though but little in compari$on of the exhau$ted, would be able to impell the the Water to a greater height then is u$ual in ordinary Filtrations: we re$olved, in$tead of a Li$t of Cotton, or the like Filtre, to make u$e of a <I>Siphon</I> of Gla$s, delineated in the third Figure, con$i$t- ing of three pieces, two $traight, and the third crooked to joyn them toge- ther; who$e Junctures were diligently clo$'d, that no Air might finde entrance at them. One of the Legs of this <I>Si- phon</I> was (as it $hould be) $omewhat longer then the other, and was pervious at the bottom of it onely, by a hole al- mo$t as $lender as a hair, that the Water might but very lea$urely drop out of it, le$t it $hould all run out before the Experiment were compleat- ed. The other and $horter Leg of the <I>Siphon</I> was quite open at the end, and of the $ame widene$$e with the <pb n=264> re$t of the Pipe, who$e bore was about <*>/4 of an Inch. The whole Siphon made up of the$e $everal pieces put together, was de$ign'd to be about a Foot and a half long; that the remaining Air, when the Ve$$el was exhau$ted after the wont- ed manner, might not be able to impell the Water to the top of the <I>Siphon;</I> which being inverted, was fill'd with Wa- ter, and of which the Shorter leg being let down two or three Inches deep into a Gla$s Ve$$el full of Water, and the up- per parts of it being fa$ten'd to the in$ide of the Cover of the Receiver, we pro- ceeded to clo$e fir$t, and then to empty the Ve$$el. <p>The effect of the tryal was this, that till a pretty quantity of Air had been drawn out, the Water dropp'd freely out at the lower end of the lower leg of the <I>Siphon,</I> as if the Experiment had been performed in the free Air. But afterwards, the Bubbles (as had been apprehended) began to di$clo$e them$elves in the Wa- ter, and a$cending to the top of the <I>Si- phon,</I> imbodyed them$elves there into one, which was augmented little by little by the ri$ing of other bubbles that from time to time broke into it, but much <pb n=278> fir$t we thought might be $ome $tain up- on the Gla$s; but after, finding it to be in divers Qualities like the Oyl, and Salt of the Concrete we were Di- $tilling, we began to $u$pect that the mo$t $ubtle and fugitive parts of the im- petuou$ly a$cending Steams, had pene- trated the $ub$tance (as they $peak) of the Gla$s, and by the cold of the am- bient Air were conden$'d on the $ur- face of it. And though we were ve- ry backward to credit this $u$pition, and therefore call'd in an Ingenious Per$on or two, both to a$$i$t us in the Ob- $ervation, and have Witne$s of its e- vent, we continued a while longer to watch the e$cape of $uch unctuous Fumes, and upon the whole matter unanimou$ly concluded, That all things con$ider'd, the $ubtle parts of the di$till'd matter being violently agitated, by the exce$- $ive heat had pa$$'d through the Pores of the Gla$s, widen'd by the $ame heat. But this having never happen'd but once in any of the Di$tillations we have either made or $een, though the$e be not a few, it is much more rea$onable to $uppo$e, that the perviou$ne$s of our Receiver to a Body much more <pb n=279> $ubtle then Air, proceeded partly from the loo$er Texture of that particular parcel of Gla$s the Receiver was made of (for Experience has taught us, that all Gla$s is not of the $ame compact- ne$s and $olidity) and partly from the enormous heat, which, together with the vehement agitation of the pene- trant Spirits, open'd the Pores of the Gla$s; then to imagine that $uch a $ub$tance as Air, $hould be able to per- meate the Body of Gla$s contrary to the te$timony of a thou$and Chymical and Mechanical Experiments, and of many of tho$e made in our Engine, e- $pecially that newly recited: Nay, by our fifth Experiment it appears, that a thin Bladder will not at its Pores give pa$$age even to rarified Air. And on this occa$ion we will annex an Ex- periment, which has made $ome of tho$e we have acquainted with it, doubt, whether the Corpu$cles of the Air be not le$$e $ubtle then tho$e of Water. <p>But without examining here the rea$onablene$$e of that doubt, we will proceed to recite the Experiment it $elf, which $eems to teach, That though Air, <pb n=280> when $ufficiently compre$$'d, may per- chance get entrance into narrower holes and crannies then Water; yet unle$s the Air be forc'd in at $uch very little holes, it will not get in at them, though they may be big enough to let Water pa$s through them. <p>The Experiment then was this: I took a fair Gla$s <I>Siphon,</I> the lower end of who$e longe$t Leg was drawn by degrees to $uch a $lenderne$s, that the Orifice, at which the Water was to fall out, would hardly admit a very $mall Pin: This <I>Si- phon</I> being inverted, the matter was $o order'd, that a little Bubble of Air was intercepted in the $lendere$t part of the <I>Siphon,</I> betwixt the little hole newly men- tion'd, and the incumbent Water, upon which, it came to pa$s, that the Air be- ing not to be forc'd through $o narrow a pa$$age, by $o light a Cylinder of Water, though amounting to the length of divers Inches, as lean'd upon it, hinder'd the further Efflux of the Water, as long as I plea$'d to let it $tay in that narrow place: whereas, when by blowing a little at the wider end of the <I>Siphon,</I> that little par- cel of Air was forc'd out with $ome Wa- ter, the remaining Water, that before <pb n=281> continu'd $u$pended, began freely to drop down again as formerly. And if you take a Gla$s Pipe, whether it be in the form of a <I>Siphon,</I> or no, that being for the mo$t part of the thickne$s of a Mans Finger, is yet towards one end $o $len- der, as to terminate in a hole almo$t as $mall as a Hor$e-hair; and if you fill this Pipe with Water, you will finde that Li- quor to drop down freely enough tho- row the $lender Extream: But if you then invert the Pipe, you will finde that the Air will not ea$ily get in at the $ame hole through which the Water pa$$'d. For in the $harp end of the Pipe, $ome Inches of Water will remain $u$pended, which 'tis probable would not happen, if the Air could get in to $ucceed it, $ince if the hole were a little wider, the Water would immediatly $ub$ide. And though it be true, that if the Pipe be of the length of many Inches, a great part of the Wa- ter will run down at the wider Orifice, yet that $eems to happen for $ome other rea- $on, then becau$e the Air $ucceeds it at the upper and narrow Orifice, $ince all the $lender part of the Pipe, and perhaps $ome Inches more, will continue full of Water. <pb n=282> <p>And on this occa$ion I remember, that whereas it appears by our fifth Experi- ment, That the Aërial Corpu$cles (ex- cept perhaps $ome that are extraordinari- ly fine) will not pa$$e thorow the Pores of a Lambs Bladder, yet Particles of Wa- ter will, as we have long $ince ob$erv'd, and as may be ea$ily try'd, by very clo$e- ly tying a little <I>Alcalizate</I> Salt (we u$'d the Calx of Tartar, made with Nitre) in a fine Bladder, and dipping the lower end of the Bladder in Water; for if you hold it there for a competent while, you will finde that there will $train thorow the Pores of the Bladder Water enough to di$$olve the Salt into a Liquor. <p>But I $ee I am $lipt into a Digre$$ion, wherefore I will not examine, whether, the Experiment I have related, proceed- ed from hence, That the $pringy Texture of the Corpu$cles of the Air, makes them le$s apt to yield and accommodate them$elves ea$ily to the narrow Pores of Bodies, then the more flexible Particles of Water; or whether it may more pro- babiy be a$crib'd to $ome other Cau$e. Nor will I $tay to con$ider how far we may hence be a$$i$ted to ghe$s at the cau$e of the a$cen$ion of Water in the $lender <pb n=283> Pipes and <I>Siphons</I> formerly mention'd, but will return to our Bubble; and take notice, That we thought fit al$o to en- deavor to mea$ure the capacity of the Bubble we had made u$e of, by filling it with Water, that we might the better know how much Water an$wered in weight to 3/4 of a Grain of Air, but not- with$tanding all the diligence that was u$ed to pre$erve $o brittle a Ve$$el, it broke before we could perfect what we were about, and we were not then pro- vided of another Bubble fit for our turn. <p>The ha$te I was in, My Lord, when I $ent away the la$t Sheet, made me forget to take notice to you of a Problem that occurr'd to my thoughts, upon the oc- ca$ion of the $low breaking of the Gla$s Bubble in our evacuated Receiver. For it may $eem $trange, $ince by our $ixth Experiment it appears, that the Air, when permitted, will by its own internal Spring expand it $elfe twice as much as <I>Mer- $ennus</I> was able to expand it, by the heat even of a candent <I>Æolipile:</I> Yet the <I>Elater</I> of the Air was $carce able to break a very thin Gla$s Bubble, and ut- <pb n=284> terly unable to break one $omewhat thic- ker, within who$e cavity it was impri- $on'd; whereas Air pent up and agitated by heat is able to perform $o much more con$iderable effects, that (not to mention tho$e of Rarefaction that are more obvi- ous) the Learned Je$uit <I>Cabæus</I> (he that <MARG><I><*>: Ni<*>: <*>: lib:</I> 4. <I><*> A- <*></I></MARG> writ of the Load-$tone) relates, That he $aw a Marble Pillar ($o va$t, that three men together with di$play'd arms could not imbrace it, and that 1000 Yoke of Oxen drawing it $everal ways with all their $trength, could not have torn it a$$under) quite broken off in the mid$t, by rea$on of $ome Wood, which hap- pening to be burnt ju$t by the Pillar, the heat proceeding from the neighboring Fire, $o rarified $ome Air or Spirituous Matter which was $hut up in the cavities of the Marble, that it broke through the $olid Body of the Stone to obtain room to expand it $elf. <p>I remember I have taken notice that probably the rea$on why the included Air did not break the hermetically $eal'd Bub- bles that remain'd intire in our emptyed Receiver, was, That the Air, being $ome- what rarefied by the Flame imploy'd to clo$e the Gla$s, its Spring, upon the re- <pb n=285> ce$s of the heat, grew weaker then before. But though we reject not that ghe$s, yet it will not in the pre$ent ca$e $erve the turn, becau$e that much $maller Gla$s bubbles exactly clo$'d, will, by the in- cluded Air (though agitated but by the heat of a very moderate Fire) be made to fly in pieces. Whether we may be a$$i$ted to $alve this Problem, by con$i- dering that the heat does from within ve- hemently agitate the Corpu$cles of the Air, and adde its a$$i$tance to the Spring they had before, I $hall not now examine: $ince I here but propo$e a Problem, and that chiefly that by this memorable Story of <I>Cabæus,</I> notice may be taken of the prodigious power of Rarefaction, which hereby appears capable of performing $tranger things then any of our Experi- ments have hitherto a$crib'd to it. <p>We $hould hence, My Lord, imme- diatly proceed to the next Experiment, but that we think it fit, on this occa$ion, to acquaint You with what $ome former tryals (though not made in our Engine) have taught us, concerning what we would have di$cover'd by the newly mention'd Bubble that broke. And this the rather, becau$e (a great part of this <pb n=286> letter $uppo$ing the gravity of the Aire) it will not be impertinent to determine more particularly then hitherto we have done, what gravity we a$cribe to it. <p>We tooke then an <I>Æolipile</I> made of copper, weighing $ix ounces, five drachms, and eight and forty graines: this being made as hot as we dur$t make it, (for feare of melting the mettle, or at lea$t the So- dar) was removed from the fire and im- mediately $topped with hard wax that no Aire at all might get in at the little hole wont to be left in <I>Æolipiles</I> for the fumes to i$$ue out at: Then the <I>Æolipile</I> being $uffer'd lea$urely to coole was again weighed together with the wax that $topt it, and was found to weigh (by rea$on of the additionall weight of the wax) $ix ounces, $ixe drachmes, and 39 graines. La$tly, the wax being perforated without taking any of it out of the Scale, the externall Aire was $uffered to ru$h in (which it did with $ome noy$e) and then the <I>Æolipile</I> and wax, being againe weighed amounted to $ix ounces, $ix drachmes, and 50. graines. So that the <I>Æolipile</I> freed as farre as our fire could free it, from it's Aire, weighed le$$e then <pb n=287> it $elfe when repleni$hed with Air, full eleven graines. That is, the Air contain- able within the cavity of the <I>Æolipile</I> a- mounted to eleven graines and $omewhat more; I $ay $omewhat more, becau$e of the particles of the Air, that were not driven by the fire out of the <I>Æolipile.</I> And by the way (if there be no mi$take in the ob$ervations of the diligent <I>Mer- $ennus</I>) it may $eeme $trange that it $hould $o much differ from 2. or 3. of ours; in none of which we could rarifie the Air in our Æ<I>olipile</I> (though made red hot almo$t all over, and $o immediately plung'd into cold water) to halfe that degree which he mentions, namely to 70. times it's natu- rall extent, unle$$e it were that the <I>Æo- lipile</I> he imploy'd was able to $u$taine a more vehement heat then ours (which yet we kept in $o great an one, that once the $oder melting, it fell a$under into the two Hemi$pheres it con$i$ts of.) <p>The fore-mentioned way of weighing the Air by the help of an <I>Æolipile,</I> $eems $omewhat more exact then that which <I>Mer$ennus</I> u$ed, In that in ours the <I>Æoli- pile</I> was not weighed, till it was cold; whereas in his, being weighed red hot, it <pb n=288> $ubject to loo$e of it's $nb$tance in the cooling, for (as we have el$ewhere noted on another occa$ion) Copper heated red hot is wont in the cooling to throw off little thin $cales in $uch plenty, that having purpo$ely watcht a Copper <I>Æolipile</I> du- ring its refrigeration, we have $een the place round about it almo$t covered with tho$e little $cales it had every way $cat- ter'd: which, however they amount not to much, ought not to be over-looked, when 'tis $o light a body as Air, that is to be weighed. We will not examine, whether the Æ<I>olipile</I> in cooling may not receive $ome little increment of weight, either from the vapid or $aline Steames that wander up and downe in the Air: But we will rather mention, that (for the grea- ter exactne$$e) we imployed to weigh our <I>Æolipile,</I> both when fill'd onely with Air and when repleni$ht with Water, a paire of $cales that would turne (as they $peak) with the fourth part of a grain. <p>As to the proportion of weight be- twixt Air and Water, $ome learned men have attempted it by wayes $o unaccurate that they $eeme to have much mi$taken it. For (not to mention the improbable accounts of <I>Kepler</I> and others.) The l<*>ar- <pb n=289> ned and diligent <I>Ricciolus,</I> having pur- po$ely endeavoured to inve$tigate this proportion by meanes of a thin blad- der, e$timates the weight of the Air to that of the Water to be as one to ten thou$and, or thereabouts. And indeed I re- member that having formerly, on a cer- tain occa$ion, weighed a large bladder full of Air, and found it when the Air was all $quee$ed out, to have contained fourteen graines of Air. I found the $ame bladder afterwards fill'd with water to containe very neer 14. pound of that liquor: accor- ding to which account, the proportion of Air to Water was almo$t as a graine to a pound, that is, as one to above 7600. To this we may adde, that on the other $ide, <I>Galileo</I> him$elfe u$ing another, but an un- accurate way too, defined the Air to be in weight to Water, but as one to 4. hun- dred. But the way formerly propo$ed of weighing the Air by an Æ<I>olipile,</I> $eemes by great oddes more exact; and (as farre as we could ghe$$e) $eemed to agree well enough with the experiment made in our Receiver. Wherefore it will be be$t to tru$t our Æ<I>olipile</I> in the enquiry we are a- bout, and according to our ob$ervations the water it contained amounting to one <pb n=290> and twenty ounces and an halfe, and as much Air as was requi$ite to fill it weigh- ing eleven graines, the proportion in gra- vity of Air to Water of the $ame bulk will be as one to 938. And though we could not fill the Æ<I>olipile</I> with water, $o exactly as we would, yet in regard we could not either as perfectly as we would, drive the Air out of it by heat; we think the proportion may well enough hold: but tho$e that are delighted with round numbers (as the phra$e is) will not be much mi$taken if they reckon water to be neere a thou$and times heavier than Air. And (for further proof that we have made the proportion betwixt the$e two bodies rather greater then le$$er then indeed it is; and al$o to confirme our former ob$erva- tion of the weight of the Air) we will adde, That, having another time put $ome Wa- ter into the Æ<I>olipile</I> before we $et it on the fire, that the copious vapours of the rarefied liquor might the better drive out the Air, we found, upon try all carefully made, that when the Æ<I>olipile</I> was refrige- rated, and the included vapours were by the cold turned againe into water (which could not have happen'd to the Air, that the preceeding Steams expell'd) the Air, <pb n=291> when it was let in, increa$'d the weight of the <I>Æolipile</I> as much as before, namely, Eleven Grains; though there were alrea- dy in it twelve Drachmes and a half, be- $ides a couple of Grains of Water, which remain'd of that we had formerly put in- to it to drive out the Air. <p><I>Mer$ennus</I> indeed tells us, that by his account Air is in weight to Water, as 1 to 1356. And adds, that we may, without any danger, believe that the gravity of Water to that of Air of a like bulk, is not le$s then of 1300 to 1. And con$e- quently, that the quantity of Air to a quantity of Water equiponderant there- to, is as 1300 to 1. But why we $hould relinqui$h our own carefully repeated try- als, I $ee not. Yet I am unwilling to re- ject tho$e of $o accurate and u$eful a Wri- ter: And therefore $hall propo$e a way of reconciling our differing Ob$ervations, by pre$enting, that the di$crepance be- tween them may probably ari$e from the differing con$i$tence of the Air at <I>London</I> and at <I>Paris:</I> For our Air being more cold and moi$t, then that which Your Lord- $hip now breaths, may be $uppo$'d al$o to be a fourth or fifth part more heavy. I leave it to be con$ider'd, whether it be of <pb n=292> any moment that our Ob$ervations were made in the mid$t of Winter, whereas his were perhaps made in $ome warmer time of the Year. But I think it were not a- mi$s that, by the method formerly pro- po$'d, the gravity of the Air were ob- $erv'd both in $everal Countries, and in the $ame Country, in the $everal Sea$ons of the Year and differing Temperatures of the Weather. And I would give $ome- thing of value to know the weight of $uch an <I>Æolipile</I> as ours full of air in the mid$t of Winter in <I>Nova Zembla,</I> if that be true which we formerly took notice of, namely, That the <I>Hollanders,</I> who Win- tered there, found that Air $o thick that their Clock would not go. <p>If Your Lord$hip $hould now ask me, if I could not by the help of the$e, and our other Ob$ervations, decide the Con- trover$ies of our Modern Mathematici- ans about the height of the Air or Atmo- $phere, by determining how high it doth indeed reach: I $hould an$wer, That though it $eems ea$ie enough to $hew that divers Famous and Applauded Writers have been mi$taken in a$$igning the heigth of the Atmo$phere: Yet it $eems very difficult preci$ely to define of what height <pb n=293> it is. And becau$e we have hitherto but lightly touch'd upon a matter of $uch im- portance, we pre$ume it wil not be thought impertinent, upon this occa$ion, to annex $omething towards the Elucidation of it. <p>What we have already try'd and newly $et down, allows us to take it for granted, that (at lea$t about <I>London</I>) the propor- tion of gravity betwixt Water and Air, of equal bulk, is as of a thou$and to one. <p>The next thing therefore that we are to enquire after, in order to our pre$ent de$ign, is the difference in weight betwixt Water and Quick-$ilver: And though this hath been defin'd already by the Il- lu$trious <I>Verulam,</I> and $ome other inqui- $itive Per$ons, that have compar'd the weight of $everal Bodies, and ca$t their Ob$ervations into Tables, yet we $hall not $cruple to annex our own tryals about it: Partly, becau$e we finde Authors con$iderably to di$-agree; partly, becau$e we u$'d exacter Scales, and a $omewhat more wary method then others $eem to have done: And partly al$o, becau$e ha- ving pro$ecuted our inquiry by two or three $everal ways; the $mall difference <pb n=294> between the events may a$$ure us that we were not much mi$taken. <p>We took then a Gla$s Pipe, of the form of an inverted <I>Siphon,</I> who$e $hape is delineated in the $ixteenth Figure: And pouring into it a quantity of Quick $ilver, we held it $o, that the $uperficies of the Liquor, both in the longer and $horter leg, lay in a Horizontal Line, denoted in the Scheme by the prick'd Line EF; then pouring Water into the longer Leg of the <I>Siphon,</I> till that was almo$t fill'd, we ob- $erv'd the $urface of the Quick-$ilver in that leg to be, by the weight of the Wa- ter, depre$$'d, as from E to B; and in the $horter leg, to be as much impell'd upward as from F to G: Whereupon ha- ving formerly $tuck marks, as well at the point B, as at the oppo$ite point D, we mealur d both the di$tance DC to have the height of the Cylinder of Quick-$il- ver, which was rai$'d above the Point D (level with the $urface of the Quick-$ilver in the other leg) by the weight of the Wa- ter, and the di$tance BA which gave us the height of the Cylinder of Water. So that the di$tance DC amounting to (2 1<*>/54) Inches, and the height of the Water a- mounting (30 45/51) Inches; and the whole <pb n=295> numbers on both $ides, which the annex- ed Fractions being reduc'd to improper Fractions of the $ame denomination, the proportion appear'd to be (the denomi- nators beng left out as equal on both $ides) as 121 to 1665; or by reduction, as one to (13 92/121). <p>Be$ides this unu$ual way of determi- ning the gravity of $ome things, we mea- $ur'd the proportion betwixt Quick-$ilver and Water, by the help of $o exact a bal- lance, as loo$es its <I>Æquilibrium</I> by the hundredth part of a Grain. But becau$e there is wont to be committed an over- $ight in weighing Quick-$ilver and Wa- ter, e$pecially if the Orifice of the Ve$$el wherein they are put be any thing wide, in regard that men heed not that the $urface of Water in Ve$$els will be concave, but that of Quick-$ilver, notably convex or protuberant: To avoid this u$ual over- $ight (I $ay) we made u$e of a gla$s bubble, blown very thin at the Flame of a Lamp, that it might not be too heavy for the Ballance, and terminating in a very $lender neck, wherein the concavity or convexity of a Liquor could not be con$iderable: This Gla$s weighing 23 1/2 Grains, we fill'd <pb n=296> almo$t with Quick-$ilver, and fa$tning a mark over again$t the middle of the pro- tuberant Superficies as near as our Eyes could judge, we found that the Quick- $ilver alone weighed 299 <*> Grains: Then the Quick-$ilver being pour'd out, and the $ame Gla$s being fill'd as full of com- mon Water, we found the Liquor to weigh 21 7/8 Grains. Whereby it appear'd that the weight of Water to Quick- $ilver, is as one to (13 19/28): Though our Il- lu$trious <I>Verulam</I> (que$tionle$s not for want of Judgement or Care, but of ex- act In$truments) makes the proportion betwixt tho$e two Liquors to be greater then of 1 to 17. And to adde, that up- on the by, $ince Quick-$ilver and well rectified Spirit of Wine, are (how ju$tly I $ay not) accounted, the one the hea- vie$t, and the other the lighte$t of Li- quors; we thought to fill in the $ame Gla$s, and with the $ame Scales to ob- $erve the difference betwixt them, which we found to be as of 1 to (16 641/1084); where- by it appear'd, That the difference be- twixt Spirit of Wine, that may be made to burn all away, ($uch as was ours) and common Water, is as betwixt 1 and (1 44/171) <pb n=297> <p>We might here take occa$ion to ad- mire, that though Water (as appear'd by the Experiment formerly mention'd of the Pewter Ve$$el) $eems not capable of any con$iderable conden$ation, and $eems not to have inter$per$'d in it any $tore of Air; yet Quick-$ilver, of no greater bulk then Water, $hould weigh near fourteen times as much. But having onely point- ed at this as a thing worthy of con$idera- tion, we will proceed in our inquiry after the heigth of the Atmo$phere: And to avoid the trouble of Fractions, we will a$$ume that Quick-$ilver is fourteen times as heavy as Water, $ince it wants $o little of being $o. <p>Wherefore having now given us the proportion of Air to Water, and Water to Quick-$ilver, it will be very ea$ie to finde the proportion betwixt Air and Quick-$ilver, in ca$e we will $uppo$e the Atmo$phere to be uniformly of $uch a con$i$tence as the Air we weighed here below. For $ince our Engine hath $uffi- <MARG><*></MARG> ciently manife$ted that 'tis the <I>Æquili- brium</I> with the external Air, that in the <I>Torricellian</I> Experiment keeps the Quick- $ilver from $ub$iding; And $ince, by our accurate Experiment formerly mention'd, <pb n=298> it appears that a Cylinder of Mercury, able to ballance a Cylinder of the whole Atmo$phere, amounted to near about thirty Inches; and $ince, con$equently we may a$$ume the proportion of Quick- $ilver to Air to be as fourteen thou$and to one; it will follow, that a Cylinder of Air, capable to maintain an <I>Æquilibrium,</I> with a Mercurial Cylinder of two Foot and an half in height, mu$t amount to 35000 Feet of our Engli$h Mea$ure; and con$equently (reckoning five Foot to a Geometrical Pace, and one thou$and $uch Paces to a Mile) to $even full Miles. <p>But this (as we lately intimated) pro- ceeds upon the $uppo$ition, that the Air is every where of the $ame con$i$tence that we found it near the $urface of the Earth; but that cannot with any $afety be concluded, not onely for the rea$on I finde to have been taken notice of by the Antients, and thus expre$t in <I>Seneca: Omnis Aër</I> ($ays he) <I>quo propior e$t terris</I> <MARG><*> 4. <*> 10.</MARG> <I>hoc cra$sior; quemadmodum in aqua & in omni humore fæx ima e$t, it a in Aëre $pi$- $ißima quæ&queacute; de$idunt;</I> but much more, becau$e the $pringy Texture of the Aërial Corpu$cles, makes them capable of a <pb n=299> very great compre$$ion, which the weight of the incumbent part of the Atmo- $phere is very $ufficient to give tho$e that be undermo$t and near the $urface of the Earth. And if we recall to minde tho$e former Experiments, whereby we have manife$ted, That Air, much rarefied with- out heat, may ea$ily admit a further ra- refaction from heat; and that the Air, even without being expanded by heat, is capa- ble of being rarefied to above one hundred and fifty times the extent it u$ually po$- $e$$es here below; How can it be demon- $trated that the Atmo$phere may not, for ought we know, or at lea$t for ought can be determin'd by our Statical and Mecha- nical Experiments, ri$e to the height of Five and twenty <I>German</I> Leagues, if not of $ome hundred of common Miles? <p>And this conjecture it $elf may appear very injurious to the height whereunto Exhalations may a$cend, if we will allow <MARG><*></MARG> that there was no mi$take in that $trange Ob$ervation made at <I>Tolous</I> in a clear Night in <I>Augu$t,</I> by the diligent Ma- thematician <I>Emanuel Magnan,</I> and thus Recorded by <I>Ricciolus,</I> (for I have not at hand the Authors own Book) <I>Vidit</I> ($ays he) <I>ab hor a undecima po$t meridiem u$&queacute; ad</I> <pb n=300> <I>mediam noctem Lunâ infra horizontem po$itâ, nubeculam quandam lucidam prope Meridianum fere u$que ad Zenith diffu$am quæ con$ider at is omnibus non poter at ni$i à $ole illuminari; ideoque altior e$$e debuit tota umbr a terræ. Addit</I> (continues <I>Ricci- olus) $imile quid eveni$$e Michaeli Angelo Riccio apud Sabinos ver$anti nempe viro in Mathe$i eruditi$simo.</I> <p>Various Ob$ervations made at the feet, tops, and interjacent parts of high Mountains, might perchance $omewhat a$$i$t us to make an e$timate in what pro- portion, if in any certain one, the higher Air is thicker then the lower, and ghe$s at the di$-form con$i$tence, as to laxity and compactne$s of the Air at $everal di$tances from us. And if the difficul- ties about the refractions of the Cele$tial Lights, were $atisfactorily determin'd, that might al$o much conduce to the pla- cing due limits to the Atmo$phere (who$e Dimen$ions tho$e Ob$ervations about Refractions $eem hitherto much to con- tract.) But for the pre$ent we dare not pronounce any thing peremptorily con- cerning the height of it, but leave it to further inquiry: contenting our $elves to have manife$ted the mi$take of divers <pb n=301> eminent Modern Writers, who will not allow the Atmo$phere to exceed above two or three Miles in height (as the Fa- mous K<I>epler</I> will not the <I>Aër refractivus</I>) and to have rendred a rea$on why in the mention we made in the Notes upon the fir$t Experiment, touching the height of the Atmo$phere, we $crupled not to $peak of it, as if it might be many Miles high. <p>WE will now proceed to recite a <MARG><I>Experi- ment</I> 37.</MARG> <I>Phænomenon,</I> which, though made among$t the fir$t, we thought fit not to mention till after many others, that we might have the opportunity to ob- $erve as many Circum$tances of it as we could, and $o pre$ent Your Lord$hip at once, mo$t of what we at $everal times have taken notice of concerning $o odde a <I>Phænomenon.</I> <p>Our Engine had not been long fini$h'd, when, at the fir$t lea$ure we could $teal from our occa$ions to make tryal of it, we cau$'d the Air to be pump'd out of the Receiver; and whil'$t I was bu$ied in entertaining a Learned Friend that ju$t then came to vi$it me, an Ingenious By- <pb n=302> $tander, thought he perceiv'd $ome new kind of Light in the Receiver, of which giving me ha$tily notice, my Friend and I pre$ently ob$erv'd, that when the Suc- ker was drawn down, immediately upon the turning of the Key, there appear'd a kinde of Light in the Receiver, almo$t like a faint fla$h of Lightening in the Day-time, and almo$t as $uddenly did it appear and vani$h. Having, not with- out $ome amazement, ob$erv'd divers of the$e Apparitions of Light, we took notice that the Day was clear, the hour about ten in the Morning, that the onely Window in the Room fac'd the North; and al$o, that by interpo$ing a Cloak, or any opacous Body between the Receiver and the Window, though the re$t of the Room were $ufficiently enlightned, yet the fla$hes did not appear as before, un- le$s the opacous Body were remov'd. But not being able on all the$e Circum- $tances to ground any firm Conjecture at the cau$e of this $urpri$ing <I>Phænome- non,</I> as $oon as Night was come, we made the Room very dark; and plying the Pump, as in the Morning, we could not, though we often try'd, find, upon the turning of the Key, $o much as the <pb n=303> lea$t glimmering of Light; whence we inferr'd, that the fla$h appearing in the Receiver, did not proceed from any new Light generated there, but from $ome reflections of the light of the Sun, or other Luminous Bodies plac'd without it; though whence that Reflection $hould proceed, it po$'d us to conje- cture. <p>Wherefore the next Morning, ho- ping to inform our $elves better, we went about to repeat the Experiment, but though we could as well as former- ly exhau$t the Receiver, though the place wherein we made the tryal was the very $ame; and though other Circum- $tances were re$embling, yet we could not di$cover the lea$t appearance of Light all that Day, nor on divers o- thers on which tryal was again fruitle$- ly made; nor can we to this very time be $ure a Day before hand that the$e Fla$hes will be to be $een in our great Receiver. Nay, having once found the Engine in a good humour (if I may $o $peak) to $hew this trick, and $ent notice of it to our Learned Friend Doctor <I>Wallis,</I> who expre$$'d a great <pb n=304> de$ire to $ee this <I>Phænomenon,</I> though he were not then above a Bow-$hoot off, and made ha$te to $atisfie his Curio$ity; yet by that time he was come, the thing he came for was no longer to be $een; $o that having vainly endeavored to exhibit again the <I>Phænomenon</I> in his pre$ence, I began to apprehend what he might think of me, when unexpectedly the Engine pre$ented us a fla$h, and after that a $econd, and as many more, as $uffic'd to $atisfie him that we might very well confidently relate, that we have our $elves $een this <I>Phænomenon,</I> though not confidently pro- mi$e to $hew it others. <p>And this un$ucce$sfulne$s whereto our Experiment is lyable, being $uch, that by all our watchfulne$s and tryals, we could never reduce it to any certain Rules or Ob$ervations; $ince in all con$titutions of the Weather, times of the Day, <I>&c.</I> it will $ometimes an$wer, and $ometimes di$-appoint our Expectations; We are much di$courag'd from venturing to frame an <I>Hypothe$is</I> to give an account of it: which if the Experiment did con$tantly $ucceed, might the more hopefully be at- tempted; by the help of the following <I>Phænomena</I> laid together: $ome of them <pb n=305> produc'd upon tryals purpo$ely made to examine the validity of the conjectures, other tryals had $ugge$ted. <p>Fir$t then we ob$erv'd, that the Appa- rition of Light may be made as well by Candle-light, as by Day-light; and in whatever po$ition the Candle be held, in reference to the Receiver, as on this or that hand of it, above it, beneath it, or any other way, provided the Beams of Light be not hinder'd from falling upon the Ve$$el. <p>Next, we noted that the fla$h appears immediately upon the turning of the Key, to let the Air out of the Receiver into the empty'd Cylinder, in $o much that I remember not that when at any time in our great Receiver, the Stop-cock was open'd before the Cylinder was ex- hau$ted (whereby it came to pa$s that the Air did rather de$cend, then ru$h into the Cylinder) the often mention'd fla$h ap- pear'd to our eyes. <p>Yet, we further ob$erv'd, that when in- $tead of the great Receiver we made u$e of a $mall Gla$s, not containing above a pound and a half of Water, the <I>Phæno- menon</I> might be exhibited though the Stop-cock were open, provided the <pb n=306> Sucker were drawn nimbly down. <p>We noted too, that when we began to empty the Receiver, the appearances of Light were much more con$picuous then towards the latter end, when little Air at a time could pa$s out of the Re- ceiver. <p>We ob$erv'd al$o, that when the Suc- ker had not been long before well Oyl'd, and in$tead of the great Receiver, the $maller Ve$$el above-mention'd was em- ploy'd; We ob$erv'd, I $ay, that then, upon the opening of the Stop-cock, as the Air de$cended out of the Gla$s in- to the empty'd Cylinder, $o at the $ame time there a$cended out of the Cylinder into the Ve$$el a certain Steam, which $eem'd to con$i$t of very little Bubbles, or other minute Corpu$cles thrown up from the Oyl, rarefied by the attrition it $uffered in the Cylinder. For at the $ame time that the$e Steams a$cended into the Gla$s, $ome of the $ame kinde manife$tly i$$ued out like a little Pillar of Smoke at the Orifice of the Valve, when that was occa$ionally open'd. And the$e Steams frequently enough pre$enting them$elves to our view, we found, by expo$ing the Gla$s to a clear Light, that <pb n=307> they were wont to play up and down in it, and $o by their whitei$hne$s, to e- mulate in $ome mea$ure the apparition of Light. <p>For we likewi$e $ometimes found, by watchful ob$ervation, that when the Fla$h was great, not onely at the very in$tant the Receiver lo$t of its tran$pa- rency, by appearing full of $ome kinde of whiti$h $ub$tance; but that for $ome $hort time after the $ides of the Gla$s continued $omewhat opacous, and $eem'd to be darken'd, as if $ome whiti$h Steam adher'd to the in$ide of them. <p>He that would render a Rea$on of the <I>Phænomenon,</I> whereof all the$e are not all the Circum$tances, mu$t doe two things; whereof the one is diffi- cult, and the other little le$s then im- po$$ible: For he mu$t give an Ac- count not onely whence the appearing whitene$s proceeds, but wherefore that whitene$s does $ometimes appear and $ometimes not. <p>For our part, we freely confe$$e our $elves at a lo$$e about rendering <pb n=308> a Rea$on of the le$s difficult part of the Problem: And though Your Lord- $hip $hould ev'n pre$s us to declare what Conjecture it was, that the above-recited Circum$tances $ugge$ted to us, we $hould propo$e the thoughts we then had, no o- therwi$e then as bare Conjectures. <p>In ca$e then our <I>Phænomenon</I> had con- $tantly and uniformly appear'd, we $hould have $u$pected it to have been produc'd after $ome $uch manner as follows. <p>Fir$t, we ob$erv'd that, though that which we $aw in our Receiver $eem'd to be $ome kinde of Light, yet it was indeed but a whitene$s which did (as hath alrea- dy been noted) opacate (as $ome $peak) the in$ide of the Gla$s. <p>Next we con$ider'd, that our com- mon Air abounds with Particles or little Bodies, capable to reflect the Beams of Light. Of this we might ea$ily give di- vers proofs, but we $hall name but two: The one, that vulgar ob$ervation of the Motes that appear in Multitudes $wim- ming up and down in the Air, when the Sun-beams $hooting into a Room, or any other $hady Place di$cover them, though otherwi$e the eye cannot di$tingui$h them <pb n=309> from the re$t of the Air: The other proof we will take from what we (and no doubt very many others) have ob$erv'd, touch- ing the Illumination of the Air in the Night. And we particularly remember, that, being at $ome di$tance from <I>London</I> one Night, that the People, upon a very well-come Occa$ion, te$tified their Joy by numerous Bon-fires; though, by rea- $on of the Interpo$ition of the Hou$es, we could not $ee the Fires them$elves, yet we could plainly $ee the Air all enlighten'd over and near the City; which argu'd, that the lucid Beams $hot upwards from the Fires, met in the Air with Corpu$cles opacous enough to reflect them to our Eyes. <p>A third thing that we con$idered, was, That white may be produc'd (without excluding other ways, or denying invi$i- ble Pores in the $olide$t Bodies) when the continuity of a Diaphanous Body happens to be interrupted by a great num- ber of Surfaces, which, like $o many little Looking-gla$$es, do confu$edly re- pre$ent a multitude of little and $eeming- ly contiguous Images of the elucid Body. We $hall not in$i$t on the explanation of this, but refer You for it to what we have <pb n=310> $aid in another Paper (touching Co- lours.) But the In$tances that $eem to prove it are obvious: For Water or whites of Eggs beaten to froth, do lo$e their tran$parency and appear white. And ha- ving out of one of our le$$er Receivers carefully drawn out the Air, and $o order'd it, that the hole by which the Water was to get in, was exceeding $mall, that the Liquor might be the more broken in its pa$$age thorow it, we ob$erv'd with plea- $ure, That, the Neck being held under Water, and the little hole newly men- tion'd being open'd, the Water that ru$h'd in was $o broken, and acquired $uch a mul- titude of new Surfaces, that the Receiver $eem'd to be full rather of Milk then Wa- ter. We have likewi$e found out, That by heating a lump of Cry$tal to a certain degree, and quenching it in fair Water, it would be di$continu'd by $uch a multi- tude of Cracks, (which created new Sur- faces within it) that though it would not fall a$under, but retain its former $hape, yet it would lo$e its tran$parency, and ap- pear white. <p>Upon the$e Con$iderations, My Lord, and $ome others, it $eem'd not ab$ur'd to imagine, That upon the ru$hing of the Air <pb n=311> out of the Receiver into the empty'd Cy- linder, the Air in the Receiver being $ud- denly and vehemently expanded, the Tex- ture of it was as $uddenly alter'd, and the parts made $o to $hift places (and perhaps $ome of them to change po$tures) as du- ring their new and vehement Motion and their varied Scituation, to di$turb the wonted continuity and $o the Diapha- neity of the Air; which (as we have alrea- dy noted) upon its cea$ing to be a tran- $parent Body, without the interpo$ition of colour'd things, mu$t ea$ily degene- rate into white. <p>Several things there were that made this Conjecture $eem the le$s improba- ble. As fir$t, That the whitene$s al- ways appear'd greater when the Ex$ucti- on began to be made, whil'$t there was $tore of Air in the Receiver, then when the Air was in great part drawn out. And next, That, having exhau$ted the Re- ceiver, and apply'd to the hole in the Stop-cock a large bubble of clear Gla$s, in $uch a manner, that we could at plea$ure let the Air pa$s out at the $mall Gla$s into the great one, and ea$ily fill the $mall one with Air again, We ob$erv'd with plea$ure, <pb n=312> That upon the opening the pa$$age be- twixt the two Gla$$es, the Air in the $maller having $o much room in the great- er to receive it, the Di$$ilition of that Air was $o great, that the $mall Viol $eem'd to be full of Milk; and this Expe- riment we repeated $everal times. To which we may adde, That, having pro- vided a $mall Receiver, who$e upper Ori- fice was $o narrow that I could $top it with my Thumb, I ob$erv'd, that when upon the Ex$uction of the Air the capacity of the Gla$s appear'd white, if by a $udden removal of my Thumb I let in the out- ward Air, that whitene$s would imme- diately vani$h. And whereas it may be objected, That in the In$tance formerly mention'd, Water turning from per$pi- cuous to white, there intervenes the Air, which is a Body of a Heterogeneous na- ture, and mu$t turn it into Bubbles to make it lo$e its tran$parency. We may borrow an An$wer from an Experiment we deliver in another Treati$e, where we teach how to make two very volatile Li- quors, which being gently put together are clear as Rock-water, and yet will al- mo$t in a moment, without the $ub-ingre$- $ion of Air to turn them into Bubbles, $o <pb n=313> alter the di$po$ition of their in$en$ible parts, as to become a white and con$i$tent Body. And this happens not as in the precipitation of <I>Benjamin,</I> and $ome o- ther Re$inous Bodies, which being di$- $olv'd in Spirit of Wine, may, by the effu- $ion of fair Water, be turn'd into a $eem- ingly Milky $ub$tance. For this white- ne$s belongs not to the whole Liquor, but to the Corpu$cles of the di$$olv'd Gum, which after a while $ub$iding leave the Li- quor tran$parent, them$elves onely re- maining white: Whereas in our ca$e, 'tis from the vary'd texture of the whole for- merly tran$parent fluid Body, and not from this or that part that this whitene$$e re$ults: For the Body is white thorowout, and will long continue $o; and yet may, in proce$s of time, without any addition, be totally reduc'd into a tran$parent Bo- dy as before. <p>But be$ides the Conjecture in$i$ted on all this while, we grounded another upon the following Ob$ervation, which was, That having convey'd $ome $moke into our Receiver plac'd again$t a Window, we ob$erv'd, that upon the ex$uction of the Air, the Corpu$cles that were $wimming in it, did manife$tly enough make the Re- <pb n=314> ceiver $eem more opacous at the very moment of the ru$hing out of the Air: For con$idering that the whitene$s, who$e cau$e we enquire of, did but $ometimes ap- pear, it $eem'd not impo$$ible but that at $uch times the Air in the Receiver might abound with Particles, capable of re- flecting the Light in the manner requi$ite to exhibit a white colour, by their being put into a certain unu$ual Motion. As may be in $ome mea$ure illu$trated by this, That the new motion of the fre$hly mention'd Fumes, made the in$ide of the Receiver appear $omewhat darker then before: And partly by the nature of our formerly mention'd $moking Liquor, who$e parts though they $eem'd tran$pa- rent whil'$t they compo$'d a Liquor, yet when the $ame Corpu$cles, upon the un- $topping of the Gla$s, were put into a new motion, and di$po$'d after a new manner, they did opacate that part of the Air they mov'd in, and exhibited a great- er whitene$s then that which $ometimes appears in our Pneumatical Ve$$el. Nor $hould we content our $elves with this $in- gle In$tance, to manife$t, That little Bo- dies, which being rang'd after one manner, are Diaphanous and Colourle$s, may, by <pb n=315> being barely agitated, di$per$'d, and con- $equently otherways rang'd, exhibite a colour, if we were not unwilling to rob our Collection of Experiments concern- ing Colours. <p>But, My Lord, I fore$ee You may make $ome Objections again$t our pro- po$ed ghe$s, which perhaps I $hall $carce be able to an$wer, e$pecially, if You in- $i$t upon having me render a Rea$on why our <I>Phænomenon</I> appears not con$tant- ly. <p>I might indeed an$wer, that probably it would do $o, if in$tead of our great Receiver we u$e $uch a $mall Viol as we have lat<I>e</I>ly mention'd, wherein the Di$$i- lition of the Air being much greater, is like to be the more con$picuous: Since I remember not that we ever made our try- al with $uch $mall Ve$$els, without find- ing the expected whitene$s to appear. But it would remain to be explicated, why in our great Receiver the <I>Phænomenon</I> $hould $ometimes be $een, and oftentimes not ap- pear. And though that Conjecture which we la$t made $hould not be rejected, yet if we were further pre$$'d to a$$ign a rea$on why the Air $hould abound with $uch Par- ticles, as we there $uppo$e, more at one <pb n=316> time then another, we are not yet pro- vided of any better An$wer, then this general one, That the Air about us, and much more that within the Receiver, may be much alter'd by $uch cau$es as few are aware of: For, not to repeat tho$e probable Arguments of this A$$ertion which we have occa$ionally mention'd here and there in the former part of this Epi$tle, we will here $et down two or three In$tances to verifie the $ame Propo- $ition. Fir$t, I finde that the Learned <I>Fo$ephus Aco$ta,</I> among other Judicious <MARG><*></MARG> Ob$ervations he made in <I>America,</I> hath this concerning the Effects of $ome Winds; <I>There are</I> ($ays he) <I>Winds which naturally trouble the Water of the Sea, and make it green, and black; others, clear as Cry$tal.</I> Next, we have ob$erv'd, That though we conveyd into the Receiver our Scales, and the <I>Pendula</I> formerly men- tion'd, clean and bright; yet after the Re- ceiver had been empty'd, and the Air let in again, the glo$s or lu$tre both of the one, and of the other, appear'd tarni$h'd by a beginning ru$t. And in the la$t place, we will $ubjoyn an Ob$ervation we made $ome Years ago, which hath been heard of by divers Ingenious Men, and $een <pb n=317> by $ome of them: We had, with pure Spirit of Wine, drawn a Tincture out of a certain Concrete which u$es to be rec- koned among Mineral Bodies; And this Tincture being very pure and tran$parent, we did, becau$e we put a great value upon it, put into a Cry$tal Viol which we care- fully $topp'd, and lock'd up in a Pre$s a- mong $ome other things that we $pecial- ly priz'd. This Liquor being a Chy- mical Rarity, and be$ides, very defecate and of a plea$ing Golden Colour; we had often occa$ion to look upon it, and $o to take notice, that one time it $eem'd to be very much troubled, and not clear as it was wont to be: Whereupon we ima- gined, that though it would be $omething $trange, yet it was not impo$$ible that $ome Precipitation of the Mineral Cor- pu$cles was then happening, and that thence the Liquor was opacated; but, finding after $ome days that though the expected Precipitation had not been made, yet the Liquor, retaining its for- mer vivid Colour, was grown clear again as before; we $omewhat wondered at it, and locking it up again in the $ame Pre$s, we re$olved to ob$erve, both whether the like changes would again appear in <pb n=318> our Tincture; and whether in ca$e they $hould appear, they would be a$cribable to the alterations of the Weather. But though, during the greate$t part of a Win- ter and a Spring, we took plea$ure to ob- $erve, how the Liquor would often grow turbid, and after a while clear again: Yet we could not finde that the$e Mutations depended upon any that were manife$t in the Air, whieh would be often dark and clouded, when the Tincture was clear and tran$parent; as on the other $ide, in clear Weather the Liquor would appear $ome- times troubled, and more opacous. So that being unable to give an account of the$e odde changes in our Tincture (which we $uppo$e we have not yet lo$t, though we know not whether it have lo$t its fickle Nature) either by tho$e of the Air, or any thing el$e that occurr'd to our thoughts; we could not but $u$pect that there may be in divers Bodies, as it were Spontaneous Mutations, that is, $uch changes as depend not upon manife$t Cau$es. But, My Lord, what has been all this while $aid concerning our <I>Phæno- menon,</I> is offer'd to You, not as contain- ing a $atisfactory Account of it, but to a$$i$t You to give Your$elf one. <pb n=319> <p>WE took a Gla$s Ve$$el, open <MARG><I>Experi- ment</I> 38.</MARG> at the top, and into it we put a mixture of Snow and common Salt ($uch a mixture as we have in another Treati$e largely di$cour$ed of) and in- to the mid$t of this mixture we $et a Gla$$e, of a Cylindrical form, clo$ely $topp'd at the lower end with Plai$ter, and open at the upper, at which we fill'd it with common Water. The$e things being let down into the Recei- ver, and the Pump being $et awork, the Snow began to melt $omewhat fa- $ter then we expected; whether upon the account of the Ex$uction of the Air, or becau$e there was but little of the Snow, or whether for any other Rea$on, it appeared doubtfull. But however, by that time the Receiver had been con$iderably exhau$ted, which was done in le$$e then 1/4 of an hour, we perceived the Water near the bot- tom of the Gla$s Cylinder to Freeze, and the Ice by a little longer $tay, $eem'd to encrea$e, and to ri$e $omewhat higher <pb n=320> then the $urface of the $urrounding Li- quor, where into almo$t all the Snow and Salt were re$olv'd. The Gla$s being ta- ken out, it appear'd that the Ice was as thick as the in$ide of the Gla$s it fill'd, though into that I could put my Thumb. The upper $urface of the Ice was very concave, which whether it were due to any unheeded accident, or to the ex$u- ction of the Air, we leave to be deter- min'd by further tryal. And la$tly, the Ice held again$t the Light, appear'd not de$titute of Bubbles, though $ome By- $tanders thought they were fewer then would have been found if the Water had been frozen in the open Air. The like Experiment we try'd al$o another time in one of our $mall Receivers, with not un- like $ucce$s. <p>And on this occa$ion, My Lord, give me leave to propo$e a Problem, which $hall be this: Whence proceeds that $trange force that we may $ometimes ob- $erve in frozen Water, to break the Bo- dies that Impri$on it, though hard and $o- lid? That there is $uch a force in Wa- ter expo$'d to Congelation, may be ga- ther'd not onely from what may be often ob$erv'd in Winter, of the bur$ting of <pb n=321> Gla$$es too clo$e $topp'd, fill'd with Wa- ter or aqueous Liquors, but by In$tances as much more con$iderable as le$s obvi- ous. For I remember, that an Ingenious Stone-cutter not long $ince complain'd to me, That $ometimes, through the negli- gence of Servants, the Rain being $uffer- ed to $oak into Marble Stones, the $uper- vening violent Fro$ts would bur$t the Stones, to the Profe$$ors no $mall dam- age. And I remember another Trades- man, in who$e Hou$e I had Lodgings, was la$t Winter complaining, that even Im- plements made of Bell-metal, being care- le$ly expo$'d to the wet, have been broken and $poil'd by the Water, which, having gotten into the little Cavities and Cran- nies of the Metal, was there afterwards frozen and expanded into Ice. And to the$e Relations, we can adde one of the <MARG><I>In <*>.</I> 4. <*></MARG> formerly mention'd <I>Cabæus's,</I> whereby they not onely may be confirm'd, but are $urpa$$'d: For he tells us, That he $aw a huge Ve$$el of exceeding hard Marble, $plit a$under by congel'd Water, who$e Rarefaction, $ays our Author, prov'd $o vehement, that the hardne$s of the Stone yielded to it; and $o a Ve$$el was broken, which would not have been $o by 100 <pb n=322> Yoke of Oxen drawing it $everal ways. I know, My Lord, that to $olve this Pro- blem, it will be $aid, That Congelation does not (as is commonly, but erroneou$ly pre$um'd) reduce water into le$s room then it po$$e$$'d before, but rather makes it take up more. And I have el$ewhere prov'd by particular Experiments, That whether or no Ice may be truly $aid to be Water rarefi'd (for that $eems que$tion- able) it may be $aid to take up more room then the Water did before Glaciation. But though we grant that freezing makes Water $well, yet, how Cold (which in Weather-Gla$$es manife$tly condences the Air) $hould expand either the Water, or the intercepted Air $o forcibly, as to perform $uch things as we have newly re- lated, will yet remain a Problem. <p>WE took an Oval Gla$s, clear and <MARG><I>Experi- ment</I> 39.</MARG> (lea$t it $hould break) pretty $trong, with a $hort Neck at the obtu$er end, through this Neck, we thru$t almo$t to the bottom, a Pipe of Gla$s, which was clo$ely Cemented to the newly mention'd Neck, the upper part of which Pipe, was drawn in $ome places more $lender <pb n=323> then a Crows Quill, that the changes of the Air in that. Gla$s Egge might be the more con$picuous; Then there was con- vey'd into the Gla$s five or $ix Spoon- fulls of Water, part of which, by blow- ing Air into the Egge, was rai$'d into the above-mention'd $lender part of the Pipe, $o that the Water was interpo$'d between the external Air, and that included in the Egge. This Weather-gla$s (delineated in the fourteenth Figure) was $o plac'd, and clo$'d up in the cavity of one of our $mall Receivers, that onely the $lender part of the Pipe, to the heigth of four or five Inches, pa$$ing thorow a hole in the Cover, remain'd expo$'d to the open Air. <p>The Pump being $et a work, upon the Ex$uction of the Air, the Water in the Pipe de$cended about a quarter of an Inch, and this upon two or three reitera- ted tryals; which $eem'd $ufficiently to argue that there was no heat produc'd in the Receiver upon the Ex$uction of the Air: For even a little heat would pro- bably have been di$cover'd by that Wea- ther-gla$s, $ince upon the bare applica- tion of my hand to the out$ide of the Receiver, the warmth having after $ome <pb n=324> time been communicated or propagated through both the Gla$$es, and the inter- val betwixt them to the Impri$on'd Air, did $o rarifie that, as to inable it, by pre$- $ing upon the $ubjacent Water, to impel that in the Pipe very many times as far as it had fallen downwards upon the Ex$ucti- on of the Air. <p>Yet $hall not we conclude, that in the cavity of the Receiver the cold was great- er after the Ex$uction of the Air then be- fore. <p>For if it be demanded what then could cau$e the fore-mention'd $ub$iding of the Water? it may be an$wered, That pro- bably it was the reaching of the Gla$s Egge, which, upon the Ex$uction of the ambient Air, was unable to re$i$t alto- gether as much as formerly the pre$$ure of the included Air, and of the Atmo$phere, which by the interven$ion of the Water, pre$$'d upon its concave $urface: Which $eem'd probable, as well by what was a- bove deliver'd, in the Experiment about the breaking of the Gla$s by the force of the Atmo$phere; as by this notable Cir- cum$tance (which we divers times ob- $erv'd) That when by drawing the Air out of the Receiver, the Water in the Pipe <pb n=325> was $ub$ided, upon the readmi$$ion of the external Air to pre$s again$t the convex $urface of the Egge, the Water was pre- $ently re-impell'd to its former height: Which would perhaps appear le$s $trange to Your Lord$hip, if You had yet $een what we have heretofore taught in ano- ther Treati$e concerning the Spring that may be di$cover'd in Gla$s, as rigid and inflexible a Body as it is generally e- $teem'd. And in the mean while it may $erve the turn to cau$e a Gla$s Egge to be blown exceeding thin, and then, having broken it, try how far you can by degrees bend $ome narrow parts of it; and how readily, upon the removal of what kept it bent, it will re$tore it $elf to its former $tate or po$ture. But to return to our Experiment, From thence it $eems pro- bable, either that there $ucceeds no Bo- dy in the room of the Air drawn out of our Receiver, or that it is not every Mat- ter that is $ubtle enough readily to pa$s through the Pores of Gla$s, that is al- ways agitated enough to produce Heat where ever it is plentifully found. So that if no <I>Vacuum</I> be to be admitted, this Ex- periment $eems to invite us to allow a great di$parity, either as to bulk, or as to <pb n=326> agitation, or as to both, betwixt $ome parts of the Etherial Sub$tance, and tho$e that are wont here below to produce Heat and Fire. <p>We try'd al$o what Operation the drawing out of the Air would have upon Camphire, that being a Body, which, though not a Liquor, con$i$ts of $uch Volatile or Fugitive parts, that without any greater agitation then that of the open Air it $elf, they will copiou$ly flie away. But we found not that even this loo$e Body was $en$ibly alter'd by the Ex$ucti- on of the ambient Air. <p>IT may $eem well worth trying, whether <MARG><I>Experi- ment</I> 40.</MARG> or no in our exhau$ted Gla$s the want of an ambient Body, of the wonted thic- ne$s of Air, would di$able even light and little Animals, as Bees, and other winged In$ects, to flie. But though we ea$ily fore$aw how difficult it would be to make $uch an Experiment; yet not to omit our endeavors, we procur'd a large Fle$h-fly, which we convey'd into a $mall Receiver. We al$o another time $hut into a great Receiver a Humming Bee, that appear'd $trong and lively, though we had rather <pb n=327> have made the tryal with a Butter-fly, if the cold Sea$on would have permitted us to finde any. <note><I>Since the writing of this XLth Experiment, we pro- cur'd a wbite Butter-Fly, and inclo$'d it in one of our $maller Receivers, where, though at fir$t he fluttered up and down, yet pre$ently, upon the ex$uction of the Air, he fell down as <*> $woon, retaining no other motion then $ome little <*>- bling of the wings.</I></note> The Fly, af- ter $ome Ex$uctions of the Air, dropp'd down from the $ide of the Gla$s whereon $he was walking: But, that the Experiment with the Bee might be the more in$tructive, we convey'd in with her a bun- dle of Flowers, which re- main'd $u$pended by a $tring near the upper part of the Receiver: And having provok'd the Bee, we excited her to flie up and down the capacity of the Ve$$el, till at length, as we de$ir'd, $he lighted upon the Flowers; whereupon we pre$ently began to draw out the Air, and ob$erv'd, That though for $ome time the Bee $eem'd to take no notice of it, yet within awhile after $he did not flie, but fall down from rhe Flowers, without appear- ing to make any u$e of her Wings to help her $elf. But whether this fall of the Bee, and the other In$ect, proceeded from the mediums being too thin for them to flie in, or barely from the weakne$s, and as it were $wooning of the Animals them$elves, you will ea$ily gather from the following Ex- periment. <pb n=328> <p>TO $atisfie our $elves in $ome mea$ure, <MARG><I>Experi- ment</I> 41.</MARG> about the account upon which Re$pira- tion is $o nece$$ary to the Animals, that Nature hath furni$h'd with Lungs, we took (being then unable to procure any other lively Bird, $mall enough to be put into the Receiver) a Lark, one of who$e Wings had been broken by a $hot, of a Man that we had $ent to provide us $ome Birds for our Experiment; but notwith- $tanding this hurt, the Lark was very lively, and did, being put into the Recei- ver, divers times $pring up in it to a good height. The Ve$$el being ha$tily, but carefully clo$'d, the Pump was diligently ply'd, and the Bird for a while appear'd lively enough; but upon a greater Ex- $uction of the Air, $he began manife$tly to droop and appear $ick, and very $oon after was taken with as violent and irregu- lar Convul$ions, as are wont to be ob- $erv'd in Poultry, when their heads are wrung off: For the Bird threw her $elf over and over two or three times, and dy- ed with her Brea$t upward, her Head downwards, and her Neck awry. And though upon the appearing of the$e Con- <pb n=329> vul$ions, we turn'd the Stop-cock, and let in the Air upon her, yet it came too late; whereupon, ca$ting our eyes upon one of tho$e accurate Dyals that go with a <I>Pendulum,</I> and were of late ingeniou$ly invented by the Noble and Learned <I>Hu- genius,</I> we found that the whole Tragedy had been concluded within ten Minutes of an hour, part of which time had been im- ploy'd in cementing the Cover to the Re- ceiver. Soon after we got a Hen-$par- row, which being caught with Bird-lime was not at all hurt; when we put her into the Receiver, almo$t to the top of which $he would briskly rai$e her $elf, the Ex- periment being try'd with this Bird, as it was with the former, $he $eem'd to be dead within $even minutes, one of which were imploy'd in cementing on the Co- ver: But upon the $peedy turning of the Key, the fre$h Air flowing in, began $low- ly to revive her, $o that after $ome pant- ings $he open'd her eyes, and regain'd her feet, and in about a 1/4 of an hour, after threatned to make an e$cape at the top of the Gla$s, which had been un$topp'd to let in the fre$h Air upon her: But the Re- ceiver being clo$'d the $econd time, $he <pb n=330> was kill'd with violent Convul$ions, within five Minutes from the beginning of the Pumping. <p>A while after we put in a Mou$e, new- ly taken, in $uch a Trap as had rather af- frighted then hurt him; vvhil'$t he vvas leaping up very high in the Receiver, vve fa$ten'd the Cover to it, expecting that an Animal u$ed to live in narrow holes vvith very little fre$h Air, vvould endure the vvant of it better then the lately men- tion'd Birds: But though, for a vvhile af- ter the Pump vvas $et avvork, he conti- nued leaping up as before; yet 'tvvas not long ere he began to appear $ick and gid- dy, and to $tagger, after vvhich he fell dovvn as dead, but vvithout $uch violent Convul$ions as the Birds died vvith. Whereupon, ha$tily turning the Key, we let in $ome fre$h Air upon him, by vvhich he recovered, after a vvhile, his $en$es and his feet, but $eem'd to continue vveak and $ick: But at length, grovving able to skip as formerly, the Pump vvas plyed again for eight minutes, about the mid- dle of vvhich $pace, if not before, a very little Air by a mi$chance got in at the Stop-cock; and about tvvo minutes after that, the Mou$e divers times leap'd up <pb n=331> lively enough, though after about two mi- nutes more he fell down quite dead, yet with Convul$ions far milder then tho$e wherewith the two Birds expired. This alacrity $o little before his death, and his not dying $ooner then at the end of the eighth minute, $eem'd a$cribable to the Air (how little $oever) that $lipt into the Receiver. For the fir$t time, tho$e Con- vul$ions (that, if they had not been $ud- denly remedied, had immediately di$- patch'd him) $ei$'d on him in $ix minutes after the Pump began to be $et awork. The$e Experiments $eem'd the more $trange, in regard, that during a great part of tho$e few minutes the Engine could but con$iderably rarefie the Air (and that too, but by degrees) and at the end of them there remain'd in the Receiver no incon- $iderable quantity; as may appear by what we have formerly $aid of our not being able to draw down Water in a Tube, with- in much le$s then a Foot of the bottom: with which we likewi$e con$ider'd, that by the ex$uction of the Air and inter$per- $ed Vapors, there was left in the Recei- ver a $pace $ome hundreds of times ex- ceeding the bigne$s of the Animal, <*>e- ceive the fuliginous Steams, from which, <pb n=332> expiration di$charges the Lungs; and, which in the other ca$es hitherto known, may be $u$pected, for want of room, to $tifle tho$e Animals that are clo$ely pent up in too narrow Receptacles. <p>I forgot to mention, that having cau$'d the$e three Creatures to be open'd, I could, in $uch $mall Bodies, di$cover lit- tle of what we $ought for, and what we might po$$ibly have found in larger Ani- mals; for though the Lungs of the Birds appear'd very red, and as it were inflam'd, yet that colour being u$ual enough in the Lungs of $uch winged Creatures, de$erves not $o much our notice, as it does, That in almo$t all the de$tructive Experiments made in our Engine, the Animals appear'd to die with violently Convul$ive Moti- ons: From which, whether Phy$icians can gather any thing towards the Di$covery of the Nature of Convul$ive Di$tem- pers, I leave to them to con$ider. <p>Having proceeded thus far, though (as we have partly intimated already) there appear'd not much cau$e to doubt, but that the death of the fore-mention'd Ani- mals proceeded rather from the want of Air, then that the Air was over-clogg'd by the $teams of their Bodies, exqui$ite- <pb n=333> ly pent up in the Gla$s; yet I, that love not to believe any thing upon Conje- ctures, when by a not over-difficult Ex- periment I can try whether it be True or no, thought it the $afe$t way to obviate Objections, and remove Scruples, by $hut- ting up another Mou$e as clo$e as I could in the Receiver, wherein it liv'd above three quarters of an hour; and might pro- bably have done $o much longer, had not a <I>Virtuo$o</I> of quality, who in the mean while chanc'd to make me a Vi$it, de$ir'd to $ee whether or no the Mou$e could be kill'd by the ex$uction of the ambient Air, whereupon we thought fit to open, for a little while, an intercour$e betwixt the Air in the Receiver, and that without it, that the Mou$e might thereby (if it were needful for him) be refre$h d, and yet we did this without uncementing the Cover at the top, that it might not be objected, that perhaps the Ve$$el was more clo$ely $topp'd for the ex$uction of the Air then before. <p>The Experiment had this event, that after the Mou$e had liv'd ten Minutes, (which we a$crib'd to this, that the Pump, for want of having been lately Oyl'd, could move but $lowly, and could not by <pb n=334> him that manag'd it, be made to work as nimbly as it was wont) at the end of that time he dy'd with Convul$ive Fits, where- in he made two or three bounds into the Air, before he fell down dead. <p>Nor was I content with this, but for Your Lord$hips further $atisfaction, and my own, I cau$'d a Mou$e, that was very hungry, to be $hut in all Night, with a Bed of Paper for him to re$t upon: And to be $ure that the Receiver was well clo$'d, I cau$'d $ome Air to be drawn out of it, whereby, perceiving that there was no $en$ible leak, I pre$ently re-ad- mitted the Air at the Stop-cock, le$t the want of it $hould harm the little Animal; and then I cau$'d the Engine to be kept all Night by the Fire $ide, to keep him from being de$troy'd by the immoderate cold of the Fro$ty Night. And this care $ucceeded $o well, that the next Morning I found that the Mou$e not onely was a- live, but had devour'd a good part of the Chee$e that had been put in with him. And having thus kept him alive full twelve hours, or better, we did, by $ucking out part of the Air, bring him to droop, and to appear $well'd; and by letting in the Air again, we $oon reduc'd him to his for- mer liveline$s. <pb n=335> <C><I>A Digre$sion containing $ome Doubts touching Re$pi- ration.</I></C> <p>I Fear Your Lord$hip will now expect, that to the$e Experiments I $hould add my Reflections on them, and attempt, by their a$$i$tance, to re$olve the Diffi- culties that occur about Re$piration; $ince at the beginning I acknowledg'd a further Enquiry into the Nature of that, to have been my De$ign in the related Tryals. But I have yet, becau$e of the inconve- nient Sea$on of the Year, made $o few Experiments, and have been $o little $a- tisfied by tho$e I have been able to make, that they have hitherto made Re$piration appear to me rather a more, then a le$s My$terious thing, then it did before. But yet, $ince they have furni$h'd me with $ome $uch new Con$iderations, concern- ing the u$e of the Air, as confirms me in my Diffidence of the Truth of what is commonly believ'd touching that matter; That I may not appear $ullen or lazy, I am content not to decline employing a <pb n=336> few hours in $etting down my Doubts, in pre$enting Your Lord$hip $ome Hints, and in con$idering whether the Tryals made in our Engine, will at lea$t a$$i$t us to di$cover wherein the Deficiency lies that needs to be $upply'd. <p>And this, My Lord, being all my pre- $ent De$ign, I $uppo$e You will not ex- pect that (as if You knew not, or had for- gotten what Anatomi$ts are wont to teach) I $hould entertain You with a need- le$s Di$cour$e of the Organs of Re$pira- tion, and the variety of their Structure in $everal Animals; though if it were ne- ce$$ary, and had not been perform'd by o- thers, I $hould think, with <I>Galen,</I> that by <MARG><I>Galen<*> de <*>, Part: <*></I> 3.</MARG> treating of the Fabricks of living Bodies, I might compo$e Hymns to the wi$e Au- thor of Nature, who, in the excellent con- trivance of the Lungs, and other parts of (tho$e admirable Engines) Animals, ma- nife$ts him$elf to be indeed what the Elo- quent Prophet mo$t ju$tly $peaks him, <I>Wonderful in Counsel, and excellent in</I> <MARG><*>a.28.29.</MARG> <I>working.</I> <p>Nor $hall we any further meddle with tho$e Controver$ies $o much agitated a- mong the Moderns, namely, <I>Whether the motion of the Lungs in Re$piration be their</I> <pb n=337> <I>own, or but con$equent to the motion of the Thorax, Diaphragme, and</I> (as $ome Learn- ed Men would have it) <I>the Abdomen; And, Whence it is that the Air $wells the Lungs in In$piration</I> any further then they may receive light from our Engine: But that it may appear what kinde of $ervice it is that may be expected from it on this oc- ca$ion, we mu$t premi$e a few Words to $hew wherein the $trength of the Obje- ction we are to an$wer, lies. In favor then of tho$e that would have the Lungs ra- ther pa$$ive then active in the bu$ine$s of Re$piration, it may again$t the common opinion be alledg'd, That as the Lungs be- ing de$titute of Mu$cles and of Fibres, are unfit to dilate them$elves; $o it ap- pears, that without the motion of the <I>Thorax</I> they would not be fill'd with Air. Since as our Learned Friend Dr. <I>High- more</I> has well (and congruou$ly, to what our $elves have purpo$ely try'd) ob- $erv'd, if a live Dog have a great wound made in his Che$t, the Lobes of the Lungs on that $ide of the <I>Media$ti- num</I> will $ub$ide and lie $till; the <I>Tho- rax</I> and the Lobes on the other $ide of the <I>Media$tinum,</I> continuing their former motion. And if $uddenly at once <pb n=338> the Mu$cles of the Che$t be on both $ides di$$ected, upon the Ingre$s of the Air, the whole Lungs, though untouch'd, will remain movele$s, at lea$t, as to any ex- pan$ion or contraction of their $ub$tance. <p>To which we may adde the Ob$ervati- on of the diligent <I>Bartholinus,</I> who af- firms the like of the <I>Diaphragme</I> al- $o, namely, That it being wounded, the Lungs will fall together, and the Re$pi- ration cea$e, which my Experiments op- po$e not, provided the Wound be any thing great. And indeed the <I>Diaphragme</I> $eems the principal In$trument of ordina- ry and gentle Re$piration, although to re$train'd Re$piration (if I may $o call it) the interco$tal Mu$cles, and perhaps $ome others may be allowed eminently to concur. But the chief of the Contro- ver$ies formerly pointed at, is not yet de- cided, namely, what it is that conveys the Air into the Lungs. For when, to coun- terballance all that has been alledg'd, tho$e that plead for the Lungs, demand what it is that $hould bring the Air into the Lungs, if them$elves do not attract it, their Antagoni$ts di$agree about the Re- ply. For when to this que$tion $ome of the be$t Modern Philo$ophers an$wer, <pb n=339> that by the dilatation of the Che$t the contiguous Air is thru$t away, and that pre$$ing upon the next Air to it, and $o onwards, the Propul$ion is continued till the Air be driven into the Lungs, and $o dilate them: When this (I $ay) is an- $wered, it is Objected even by <I>Bartholine</I> him$elf, as a convincing Reply, that, ac- cording to this Doctrine, a Man could not fetch his Breath from a great Ve$$el full of Air, with a $lender Neck, becau$e, that when his Mouth covers the Orifice of the Neck, the dilatation of his <I>Thorax</I> could not propell the Air in the Ve$$el into his Lungs, by rea$on of its being $eparated by the inclo$ing Ve$$el from the ambient Air; and yet, $ay they, Experience wit- ne$$es that out of $uch a Ve$$el a Man may $uck Air. But of this difficulty our Engine furni$hes us with an ea$ie Solution, $ince many of the former Experiments have ma- nife$ted, That in the ca$e propo$ed, there needs not be made any (though 'tis true that in ordinary Re$piration there is wont to be made $ome) propul$ion of the Air by the $welling <I>Thorax</I> or <I>Abdomen</I> into the Lungs; $ince upon the bare Dilatation of the <I>Thorax,</I> the Spring of that internal Air, or halituous $ub$tance that is wont <pb n=340> to po$$e$s as much of the Cavity of the Che$t as the Lungs fill not up, being much weaken'd, the external and contiguous Air mu$t nece$$arily pre$s in at the open Winde-Pipe into the Lungs, as finding there le$s re$i$tance then any where el$e a- bout it. <p>And hence (by the way) we may derive a new a$$i$tance to judge of that famous Controver$ie di$puted among Naturali$ts and Phy$itians, ever $ince <I>Galens</I> time, $ome maintaining that the Che$t, with the contained Lungs, may be re$embled to a pair of Bellows, which comes therefore to be fill'd becau$e it was dilated: And o- thers pleading to have the compari$on made to a Bladder, which is therefore di- lated becau$e it is fill'd. For as to the <I>Thorax,</I> it $eems evident from what has been lately $aid, that it, like a pair of Bel- lows, happens to be partly fill'd with Air, but becau$e it was dilated: But as for the Lungs them$elves, who want Fibres to di$tend them, they may fitly enough be compar'd to a Bladder; $ince they are di- lated by being fill'd, namely, by that Air which ru$hes into them upon the dilatation of the Che$t, in who$e increa$ed Cavity it findes (as we fre$hly noted) le$s re$i$t- <pb n=341> ance to its Spring then el$ewhere. And this brings into my minde that $trange Ob$ervation of <I>Nicolaus Fontanus,</I> a Phy- <MARG><I>Fontan<*> apud</I> <*> tholin<*> cap. 9.</MARG> $itian at <I>Am$terdam,</I> who te$tifies, That in a Boy of the $ame Town, four years old, there was found, in$tead of Lungs, a certain Membranous Bladder; which be- ing fill'd with Wind, and furni$h'd with little Veins, had its origination from the Wind-Pipe it $elf; which being $uppo$'d true, how well it will agree with mo$t of the Opinions touching Re$piration, I leave to be con$idered. <p>And thus may the grand Objection of <I>Bartholine,</I> and others, be an$wered: But I leave to Anatomi$ts to con$ider what is to be $aid to $ome Ob$ervations that $eem to contradict tho$e Anatomical Experi- ments already mention'd: Such was par- ticularly that which I remember I have read in <I>Sennertus</I> (from the ob$ervation of his Father-in-law <I>Schato</I>) of a Melancho- ly Student, who having $tabb'd him$elf, and pierced the <I>Diaphragme</I> in the thinner or tendonous part (call'd by many the Nervous Circle) lived $even Moneths af- ter he had $o wounded him$elf, though af- ter his death (preceded by violent Vomit- <pb n=342> ings) the Wound (perchance dilated by tho$e $trainings) appear'd $o great, that the whole Stomack was found to have got in by it into the left $ide of the <I>Thorax.</I> And $uch al$o was the accident that hap- pen'd to a Noble Man, whom I remem- ber I have $een, and who is yet alive, in who$e Che$t there has, for the$e many years, remain'd a hole $o great, that the motion of his Heart may be perceiv'd by it. The$e (I $ay) and $ome other Ob$er- vations, I $hall now forbear to in$i$t on, becau$e I hold it not unfit, before we come to con$ider the u$e of Re$piration, that we acquaint Your Lord$hip with an Ingenious Conjecture, that was made at the cau$e of the ha$ty death of the Ani- mals our Engine kill'd: namely, That it was not the want of Air that de$troy'd them, but the Pre$$ure of the innate Air in the cavity of the Che$t; as if the Spring of this Air being no longer coun- terballanc'd by the ambient Air, was there- by become $o $trong, that it kept the <I>Thorax</I> forcibly di$tended, and hinder'd its wonted contraction; and $o compre$$'d the Lungs and their Ve$$els, as to ob$truct the Circulation of the Blood. And this <pb n=343> Conjecture, as it is $pecious enough, $o I might have admitted it for true; but that I con$ider'd, that (not to mention that one, e$pecially of the Animals kill'd in our Engine, $eem'd manife$tly for a pret- ty while, and not long before he dy'd, to move his <I>Thorax,</I> as if he exerci$'d Re$pi- ration) the diligent <I>Wallæus</I> relates, That he divers times ob$erv'd, in the Di$$ecti- on of live Bodies, that the Membrane that inve$ts the Lungs, had Pores in it as big as the larger $ort of Peas, which a- grees with the Ob$ervations of Chyrur- gions and Phy$itians, <I>viz.</I> That matter collected in the <I>Thorax,</I> has penetrated in- to the Lungs, and been di$charged by coughing. And I remember too, that mo$t of the Animals we kill'd in our Engine were Birds, of who$e Lungs <I>Harvey</I> $omewhere informs us, That he ob- $erv'd them very manife$tly to open at their Extremities into the <I>Abdomen.</I> And by $uch Perforations we may well $uppo$e the pa$$age free betwixt the exter- nal Air and that in the <I>Abdomen:</I> But this Conjecture may be further con$ider'd. Be$ides, to $how that the Animals that died in our Gla$$es, need not be $uppo$'d <pb n=344> to have been kill'd by the want of Air, we fore$ee another Argument that we mu$t deal $o ingeniou$ly with Your Lord$hip, as not to conceal. You very well know, that be$ides the generality of the Schools, there are many new Philo$ophers who, though they di$$ent from the old Peripateticks in other things, do, as they, deny the po$$ibility of a <I>Vacuum;</I> and hold, that tho$e $paces which are devoid of Air, and other gro$$er Bodies, are all of them exactly repleni$hed with a certain Etherial Matter, $o thin and $ubtle, that it can freely permeate the Pores of the compacted$t and clo$e$t Bodies, and ev'n of Gla$s it $elf. Now $ome of tho$e Na- turali$ts that are of this per$wa$ion may object, That the Animals that died in our Receivers, did $o, not $o much for lack of Air, as by rea$on that the Air that was pump'd out was nece$$arily $ucceeded by an Etherial Sub$tance; which con$i$ting of parts vehemently agitated, and $o very $mall, as without re$i$tance to pa$s in and out through the very Pores of Gla$s; it may well be $uppo$'d, that a con$iderable quantity of this re$tle$s and $ubtle Mat- ter, meeting together in the Receiver, <pb n=345> with the exce$$ive heat of it, may be quickly able to de$troy a little Animal, or at lea$t, make the Air too intemperately hot to be fit for Re$piration. <p>But though this be a Difficulty not $o ea$ily to be re$olv'd without the a$$i$tance of our Engine, yet I $uppo$e we have al- ready an$wer'd the Objection by our 38<SUP>th</SUP> and 39<SUP>th</SUP> Experiments; which though we made partly for other purpo$es, yet we premi$'d them onely to clear up the diffi- culty propo$'d. <p>Another $u$pition we $hould have en- tertain'd concerning the death of our Ani- mals, namely, That upon the $udden re- moval of the wonted pre$$ure of the am- bient Air, the warm Blood of tho$e Ani- mals was brought to an Efferve$cence or Ebullition, or at lea$t $o vehemently ex- panded, as to di$turb the Circulation of the Blood, and $o di$order the whole Oe- conomy of the Body. (This (I $ay) I $hould have had $ome $u$pition of) but that Animals of a hot Con$titution are not the $ole ones that cannot in our ex- hau$ted Engine exerci$e the Function of Life. But I mu$t not now dwell upon matters of this nature, becau$e I think it high time to proceed to the con$iderati- <pb n=346> on of the principal $ubject of our Engine, namely, The u$e of Re$piration; or ra- ther, The u$e of the Air in Re$piration. For whereas of the divers u$es of it men- tion'd by Anatomi$ts the mo$t, $uch as the Production and Modulation of the Voice by the Eli$ion of the Air, the <I>La- rynx</I> &c. the expul$ion of Excrements by Coughing, the conveying in of Odours by In$piration, and $ome others, rather convenient for the well being of an Ani- mal, then ab$olutely nece$$ary to his Life: Whereas (I $ay) the other u$es are $uch as we have $aid, The great <I>Hippocrates</I> him- $elf gives this notable Te$timony to the u$e of the Air, as to Animals endow'd with Lungs, <I>Mortalibus</I> ($ays he) <I>hic</I> ($pi- ritus) <I>tum vitæ, tum morborum ægrotis cau- $a e$t. Tantáque corporibus omnibus $pi- ritûs ine$t neceßitas, ut $iquidem aliis om- nibus & cibis & potionibus, quis <*>b$tineat, duos tam&etilde; aut tres, vel plures dies poßit vi- tam ducere: At $i quis $piritus in corpus vias intercipiat, vel exiguâ diei parte, he- mini pereundum $it; Adeo nece$$arius e$t u$us $piritûs in corpore. Ad hæc quo&queacute;, quum omnibus aliis actionibus homines qui- e$cant, quod mutationibus innumer is vita $it expo$ita, ab hâc tamen $olâ actione nun-</I> <pb n=347> <I>quam de$i$tant animantia, quin aut $piritum adducant, aut reddant.</I> <p>But touching the account upon which the In$piration and Ex$piration of Air (both which are comprehended in <G>a)gapno<*></G>, Re$piration) is $o nece$$ary to Life, both Naturali$ts and Phy$itians do $o di$agree, that it will be very difficult either to re- concile their Opinions, or determine their Controver$ies. <p>For fir$t, Many there are who think the chief (if not $ole) u$e of Re$piration to be the Cooling and tempering of that Heat in the Heart and Blood, which other- wi$e would be immoderate: And this O- pinion, not onely $eems to be mo$t recei- ved among$t Schola$tick Writers, but di- vers of the new Philo$ophers, Carte$ians, and others, admitted with $ome variation; teaching, That the Air is nece$$ary, by its coldne$s, to conden$e the Blood that pa$- $es out of the right Ventricle of the Heart into the Lungs, that thereby it may obtain $uch a con$i$tence, as is requi$ite to make it fit Fewel for the vital Fire or Flame, in the left Ventricle of the heart. And this Opinion $eems favor'd by this, That Fi$hes, and other cold Creatures, who$e Hearts have but one cavity, are al- <pb n=348> $o unprovided of Lungs, and by $ome o- ther con$iderations. But though it need not be deny'd, that the in$pir'd Air may $ometimes be of u$e by refrigerating the Heart; yet (again$t the Opinion that makes this Refrigeration, the mo$t genuine and con$tant u$e of the Air) it may be Obje- cted, That divers cold Creatures ($ome of which, as particularly Frogs, live in the Water) have yet need of Re$piration, which $eems not likely to be needed for Refrigeration by them that are de$titute of any $en$ible heat, and be$ides, live in the cold Water: That even decrepid old Men, who$e natural heat is made very languid, and almo$t extingui$h'd by rea- $on of age, have yet a nece$$ity of fre- quent Re$piration: That a temperate Air is fitte$t for the generality of breathing Creatures; and as an Air too hot, $o al- $o an Air too cold, may be inconvenient for them (e$pecially, if they be troubled with an immoderate degree of the $ame Quality which is predominant in the Air:) That in $ome Di$ea$es the natural heat is $o weaken'd, that in ca$e the u$e of Re$pi- ration were to cool, it would be more hurtful then beneficial to breath; and the $u$pending of the Re$piration, may $up- <pb n=349> ply the place of tho$e very hot Medicines that are wont to be employ'd in $uch Di- $tempers: That Nature might much bet- ter have given the Heart but a moderate heat, then $uch an exce$$ive one, as needs to be perpetually cool'd, to keep it from growing de$tructive; which the gentle, and not the burning heat of an Animals Heart, $eems not inten$e enough $o indi- $pen$ably to require. The$e, and other Objections, might be oppo$'d, and pre$$'d again$t the recited Opinion: But we $hall not in$i$t on them, but onely adde to them, That it appears not by our fore- going Experiments (I mean the 38<SUP>th</SUP> and 39<SUP>th</SUP>) that in our exhau$ted Receiver, where yet Animals die $o $uddenly for want of Re$piration, the ambient Body is $en$ibly hotter then the common Air. <p>Other Learned Men there are, who will have the very $ub$tance of the Air to get in by the Ve$$els of the Lungs, to the left Ventricle of the Heart, not onely to temper its heat, but to provide for the generation of Spirits. And the$e alledge for them$elves the Authority of the An- tients, among whom <I>Hippocrates</I> $eems manife$tly to favor their Opinion; and both <I>Ari$totle</I> and <I>Galen</I> do $ometimes <pb n=350> (for methinks they $peak doubtfully e- nough) appear inclinable to it. But for ought ever I could $ee in Di$$ections, it is very difficult to make out, how the Air is convey'd into the left Ventricle of the Heart, e$pecially the <I>Sy$tole</I> and <I>Dia$tole</I> of the Heart and Lungs, being very far from being Synchronical: Be$ides, that the Spirits $eeming to be but the mo$t $ubtle and unctuous Particles of the Blood, appear to be of a very differing Nature from that of the lean and incom- bu$tible Corpu$cles of Air. Other Ob- jections again$t this Opinion have been propo$'d, and pre$t by that excellent Ana- tomi$t, and my Indu$trious Friend, Dr. <I>Highmore,</I> to whom I $hall therefore refer you. <p>Another Opinion there is touching Re- $piration, which makes the genuine u$e of it to be Ventilation (not of the Heart, but) of the Blood, in its pa$$age thorow the Lungs; in which pa$$age, it is di$- burthened of tho$e Excrementitious Steams, proceeding, for the mo$t part, from the $uperfluous Sero$ities of the Blood, (we may adde) and of the <I>Chyle</I> too, which (by tho$e new Conduits of late very happily detected by the famous <pb n=351> <I>Pecquet</I>) hath been newly mix'd with it in the Heart.) And this Opinion is that of the Indu$trious <I>Mœbius,</I> and is $aid to have been that of that excellent Philo$o- pher <I>Ga$$endus;</I> and hath been in part an Opinion almo$t vulgar: But this <I>Hypo- the$is</I> may be explicated two ways: For fir$t, The nece$$ity of the Air in Re$pi- ration, may be $uppo$'d to proceed from hence; That as a Flame cannot long burn in a narrow and clo$e place, becau$e the Fuliginous Steams it unce$$antly throws out, cannot be long receiv'd into the am- bient Body; which after a while growing too full of them, to admit any more, $ti- fles the flame, $o that the vital Fire in the Heart requires an ambient Body, of a yielding nature, to receive into it the $u- perfluous Sero$ities and other Recrements of the Blood, who$e $ea$onable Expul$i- on is requi$ite to depurate the Ma$s of Blood, and make it fit both to Circulate; and to maintain the vital heat re$iding in the Heart. The other way of explicating the above-mention'd <I>Hypothe$is,</I> is, by $uppo$ing, that the Air does not onely, as a Receptacle, admit into its Pores the Ex- crementitious vapors of the Blood, when they are expell'd through the Wind-Pipe, <pb n=352> but does al$o convey them out of the Lungs, in regard that the in$pired Air, reaching to all the ends of the <I>A$pera Ar- teria,</I> does there a$$ociate it $elf with the Exhalations of the circulating Blood, and when tis exploded, carrys them away with it $elf, as we $ee that winds $peedily dry up the $urfaces of wet Bodies, not to $ay any thing of what we formerly ob$ervd touch- ing our Liquor, who$e fumes were $trange- ly elevated upon the Ingre$s of the Air. <p>Now of the$e two ways of explicating the u$e of Re$piration, our Engine af- fords us this Objection again$t the fir$t; That upon the Ex$uction of the Air, the Animals die a great deal $ooner then if it were left in the Ve$$el; though by that Ex$uction the ambient $pace is left much more free to receive the $teams that are ei- ther breathed out of the Lungs of the Animal, or di$charg'd by in$en$ible Tran- $piration through the Pores of his Skin. <p>But if the <I>Hypothe$is</I> propo$'d, be taken in the other $en$e, it $eems congruous e- nough to that grand ob$ervation, which partly the <I>Phænomena</I> of our Engine, and partly the relations of Travellers, have $ugge$ted to us, namely, That there is a <pb n=353> certain con$i$tence of Air requi$ite to Re- $piration; $o that if it be too thick, and already over-charged with vapors, it will be unfit to unite with, and carry off tho$e of the Blood, as Water will di$$olve, and a$$ociate to it $elf but a certain proportion of $aline Corpu$cles; and if it be too thin or rarefied, the number or $ize of the Aërial Particles is too $mall to be able to a$$ume and carry off the halituous Excre- ments of the Blood, in $uch plenty as is requi$ite. <p>Now that Air too much thicken'd (and as it were clogg'd) with Steams, is unfit for Re$piration, may appear by what is wont to happen in the Lead-Mines of <I>De- von$hire,</I> (and, for ought I know, in tho$e too of other Countrys, though I have $een Mines where no $uch thing was com- plain'd of) for I have been inform'd by more then one credible Per$on (and parti- cularly by an Ingenious Man, that has of- ten, for curio$ity, digg'd in tho$e Mines, and been imploy'd about them) that there often ri$es Damps, as retaining the <I>Ger- mane</I> Word by which they call them) which does $o thicken the Air, that unle$s the Work-men $peedily make $igns to them that are above, they would (which <pb n=354> al$o $ometimes happens) be pre$ently $tifled for want of Breath; and though their Companions do make ha$te to draw them up, yet frequently, by that time they come to the free Air, they are, as it were, in a $woon, and are a good while be- fore they come to them$elves again. And that this $wooning $eems not to proceed from any Ar$enical or Poy$onous Exhala- tion contain'd in the Damp, as from its over-much conden$ing the Air, $eems pro- bable from hence; That the $ame Damps oftentimes lei$urely extingui$h the flames of their Candles or Lamps; and from hence al$o that it appears (by many Rela- tions of Authentical Authors) that in tho$e Cellars where great $tore of new Wine is $et to work, men have been $uffo- cated by the too great plenty of the $teams exhaling from the Mu$t, and too much thickning the Air: as may be gathered from the cu$tom that is now u$ed in $ome hot Countrys, where tho$e that have oc- ca$ion to go into $uch Cellars, carry with them a quantity of well kindled Coals, which they hold near their Faces; where- by it comes to pa$s, that the Fire di$cu$- $ing the Fumes, and rarefying the Air re- duces the ambient Body to a con$i$tence fit for Re$piration.