Archimedes Texts

87
the River Arno raised by a Land-flood half a Brace, I might con
fidently affirm the said River to be raised in Pisa those six or se
ven Braces, &c. From such like accidents I conclude in the same
Letter, that it is necessary to make great account of every little
rise that Fiume morto shall make towards the Sea. Now cometh
Bartolotti (and perhaps because I knew not how to express my
self better, understandeth not my Proposition) and speaketh that
which indeed is true, but yet besides our case: Nor have I ever
said the contrary; and withall doth not apply it to his purpose.
Nay I say, that if he had well applyed it, this alone had been a
ble to have made him change his opinion. And because he saith,
that I said, that it is true, when the abatement proceedeth from
some cause above, as namely by Rain, or opening of Lakes;
But when the cause is from below, that is, by some stop, as for
instance some Fishers Wears or Locks, or some impediment re
mote from the Sea, although at the Level it shall rise some Braces
where the impediment is, yet that rising shall go upwards; and
here he finisheth his Discourse, and concludeth not any thing
more. To which I say first, that I have also said the same in the
Proposition, namely, that a Flood coming (which maketh Arno
to rise in Pisa six or seven Braces (which I take to be a superiour
cause whether it be Rain or the opening of Lakes, as best plea
seth Bartolotti) in such a case I say, and in no other (for towards
the Sea-coasts it shall not cause a rising of full half a Brace; and
therefore seeing Arno at the Sea-side to be raised by a Flood, whe
ther of Rain, or of opening of Lakes half a Brace) it may be
inferred, that at Pisa it shall be raised those six or seven Braces;
which variety, well considered, explaineth all this affair in favour
of my opinion: For the rising that is made by the impediment
placed below, of Fishing Weares and Locks, operateth at the be
ginning, raising the Waters that are neer to the impediment;
and afterwards less and less, as we retire upwards from the im
pediment: provided yet that we speak not of a Flood that com
meth by accession, but onely of the ordinary Water impeded.
But there being a new accession, as in our case, then the Water
of the Flood, I say, shall make a greater rising in the parts superi
our, far from the impediment; and these impediments shall
come to be those that shall overflow the Plains, as happened
eighteen or nineteen years ago, before the opening of Fiume
morto into the Sea, The same will certainly follow, if Fiume
morto be let into Serchio. Here I could alledge a very pretty
case that befell me in la ^{*} Campagna di Roma, neer to the Sea

side. where I drained a Bog or Fen, of the nature of the Wa
ters of Pisa, and I succeeded in the enterprize, the Waters in their
site towards the Sea abating only three Palmes, and yet in the