| Boyle, Robert New experiments physico-mechanicall, touching the spring of the air and its effects 1660 |
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we must answer, That of those which are
easily intelligible without ocular demon
stration, we can at present suggest upon
our own tryals no better then these.
First,
at the open end of the Tube the Glass
must not onely be made as even at the ed
ges as you can, but it is very conveni
ent (especially if the Tube be large) that
the bottom be every way bent inwards,
that so the Orifice, not much exceeding a
quarter of an Inch in Diameter, may be
the more easily and exactly stopp'd by the
Experimenter's finger; between which
and the Quick-silver, that there may be
no Air intercepted (as very often it hap
pens that there is) it is requisite that the
Tube be fill'd as full as possibly it can be,
that the finger which is to stop it, pressing
upon the accumulated and protuberant
Mercury, may rather throw down some,
then not finde enough exactly to keep out
the Air.
It is also an useful and compen
dious way not to fill the Tube at first
quite ful of Mercury, but to leave near the
top about a qnarter of an Inch empty; for
if you then stop the open end with your
finger, and invert the Tube that quarter
of an Inch of Air will ascend in a great
bubble to the top, and in its passage thi-
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