^o ME M O IR S of the 
the mercury did fenfibly afccnd at firft, and had almoft attained 
its greateft expanfion, before the water boiled in the fkillet ^ and 
after it had boiled, tho' it flood long over the fire, he could not 
dilcern that the moft vehement boiling had any effedl on it, above 
what appeared, when it nrft began to boil ; the mercury being 
taken out, fubfided as it cooled, and in a few hours returned to 
the mark, at which it flood before it was put into the water 5 this 
fluid, being fo fenfible of a gentle warmth, and withal not lubje£l 
to evaporate without a great degree of fire, might mofl properly 
be applied to the conftruflion of thermometers, were its expan- 
fion more confiderable: However, fmall as it is, it is fufficient to 
diflurb the precife nicety of the mercurial barometers, fliewing 
the counterpoife of the prefTure of the atmofphere by a cylinder 
of mercury 5 for if mercury be more expanded, and conlequently 
lighter in warm weather than in cold, it will necelTarily follow, that 
the lame weight of the atmofphere will require a taller cylinder 
in fummer, and a fhorter in winter to counterpoife it^ and if the 
extremity of weather doth but occafion 150th part difference, as is 
probable it doth, the efFe£l thereof on a barometer will be the 
loth of an inch, above and below the mean, or a 5th in the whole. 
3. The finaller bolt- head was filled with fpirits of wine, and 
having fet it in the fkillet of water over the fire, it was found to 
afcend gradually as the heat encreafed, but flower at firfl, and 
fafler after it was well warmed 5 at length, being arrived at a 
certain degree of heat, it would then boil with great violence, 
emitting bubbles, which, rifing in the neck of t^ie bolt-head, 
would elevate all the incumbent fpirits, till they had made their 
way thro' ; and thefe fucceeding each other very fafi:, would often 
raife the fpirits to the top of the neck, and caule it to run over 5 
lb that there was no farther proceeding with this fluid than to 
that degree of heat, which caufed this boiling, and which was 
very much fhort of that of boiling water, being almofl tolerable 
to the touch : It was however very remarkable, how exactly this 
degree of heat was determined by the expanfion of the fpirits 5 for 
immediately, as it reached a certain mark on the neck, it began 
to emit bubbles, and being taken out a little to cool, and fubfide, 
it would certainly and conflantly fall a bubbling again, when 
upon a fccond immerfion, it was arrived at the aforeiaid mark ; 
during this experiment, it appeared both by the dew on the neck, 
and by the icent in the room, that tho' the neck were about 50 
inches long, yet the fpirits did evaporate very fafi, confidering the 
fmallneis of the furface of the liquor : This degree of heat, which 
Uiade fpirits of wine begin to boil, being determined fo nicely, 
made 
