RoVAL Society. 51 
made Mr. Halk^j^ concluJe, that this might very properly be 
taken for the limits of the fcale of heat in a thermometer ^ and the 
efifea thereof in the expanilon of any other fluid being accurately 
noted, might be eafily transferred to any fort of thermometer 
whatever 5 'only it muft be obferved, that the fpirits of wine, ufed 
to this purpole, be highly re61:ified or dephlegmated, for other- 
wife the different goodnefs of the fpirits will caule them to boil 
fooner or later, anS thereby pervert the defigned exa^tnefs: And 
by the bye it may be hinted, that the boiling of fpirits fooner or 
later, may poffibly be as good a teft of their ftrength and per- 
fection as their fpecific gravity, or any other method yet ufed : The 
fpirits of wine, Mr. Halley made ufe of, were poffibly none of 
the beft, but he obferved, that at the point of boiling, they had 
encreafed a 12th part in bulk 5 which great dilatation makes it a 
liquor fufficiently adapted to our purpofe, were it not for its eva» 
poration j for the difference of the goodnefs of the fpirits, and 
becaufe that by length of time they become effcete, and lofe gra- 
dually a part of their expanfive power. 4. Several other liquors 
-may be examined after this manner, but thefe alledged may fuffice 
to (hew the different effeas of heat on different fluids 5 and that 
this power of dilating and contracting with heat and cold, is as 
fpeciiically in them as their gravity, rarefadion, ^c. but in none 
fo confpicuous, as in that rare elallic fluid the air; tor by feveral 
experiments, Mr. Halley found that the heat of fummer does 
expand the ordinary air about a 30th part 5 and the honourable 
Mr. ^oyle, in hishiftory of cold, Tit^ 18. §. 8. p. 47 5- ^He^s 
experiments, which prove that the force of the ftrongeil cold in 
England) does not contraCt the air above io part; fo that the 
fame air, which, in extreme cold occupies 12 parts of fpace, in 
very hot fummer weather, will require 13 fuch fpaces; which is 
as great an expanfion as that of fpirits of wine, when they begin 
to boil 5 for which reafon, and becauie it is lb fenfible of heat 
and cold, and becaufe it continues to exert the fame elallic power, 
after being ever fo long included, it is the properefl fluid for the 
purpole of thermometers: Now the thermometers hitherto in ufe, 
are of two forts 3 the one fliewing the different temper of heat and 
cold by the expanfion of fpirits of wine, the other by the air 3 but 
neither of them was ever lb well made or adjufted, as that it might 
be concluded, what the degrees or divilions of the faid infl:ru- 
ments did mean 5 neither were they ever otherwile graduated, but 
by fl:andards kept by each particular workman, without an/ 
agreement with, or reference to each other 3 fo that whatever 
obiervations any curious perfon may make by his thermometer, 
G a ^^ 
