Archimedes Texts

If Your Lordship should now ask me
what are the true causes of this varying al
titude of the Mercurial Cylinder; I should
not undertake to answer so difficult a que
stion, and should venter to say no more,
then that among divers possible causes to
which it may be ascribed, it would not be,
perhaps, absurd to reckon these that fol
low.

First then we may consider, 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-silver will
readily ascend almost to the very top of
it, and so take up eight or nine tenth parts,
and perhaps more of that space which it
deserted before: which would not happen
if that whole space had been full of unra
rified Air, since that (as tryal may easily
satisfie you) would not have suffer'd it
self to be thrust into so narrow a room by
so weak a pressure. So that although in
our Tube when the included Air was
heated, the Quick-silver was somewhat
depress'd: Yet there is this difference be
twixt such a Tube and common Weather
Glasses, that in these the included and the