608 PHILOSOPHICAL TRANSACTIONS. [aNNO 1692-3. 



that the sooner or later boiling of spirits, or spiritous liquors, may possibly 

 be as good a test of their strength and perfection, as their specific gravity, or 

 any other yet used. 



The spirit of wine I made use of, was possibly none of the best ; but I ob- 

 served, that at the point of boiling, it had increased a 12th part in bulk: 

 which great dilatation makes it a liquor sufficiently adapted to our purpose, 

 were it not for its evaporation, and for the difference in the goodness of the 

 spirit; and because that in length of time it becomes as it' were effete, and loses 

 gradually a part of its expansive power. 



Ail these experiments were made in the months of February and March, 

 about 4 years since, the weather being reasonably cold, and not freezing; but 

 I have not since had an opportunity to try the effect of extreme cold in con- 

 tracting these liquors; which must be deferred till some sharp winter present us 

 with a season proper for these trials. 



4. Several other liquors may be examined after this manner, but the above 

 may suffice to show the different effects of heat on different fluids ; and that 

 this power, of dilating and contracting with heat and cold, is as specifically in 

 them, as their gravity, refraction, &c. but in none is it comparably so conspi- 

 cuous as in that rare elastic fluid the air; for by several experiments that I have 

 "made, I find that the heat of summer expands the ordinary air about a 30th 

 part} and Mr. Boyle, in his History of Cold, Tit. 18, § 8, p. 475, alleges 

 his own trials, proving that the force of the strongest cold in England does not 

 contract the air above a 20th part: so that, the sum of a 20th and 30th part 

 being a 12th part, we may conclude that the same air which is extremely cold 

 occupies 12 parts of space, in very hot summer weather will require 13 such 

 spaces; which is as great an expansion as that of spirit of wine when it begins 

 to boil ; for which reason, and for its being so very sensible of warmth or cold, 

 and continuing to exert the same elastic power; after being ever so long included, 

 in my opinion it is the properest fluid for the purpose of thermometers. 



Now the thermometers hitherto in use, are of two sorts ; the one showing 

 the different temper of heat and cold by the expansion of spirits of wine, the 

 other by the air; but I cannot learn that any of them of either sort were ever 

 made or adjusted, so as it might be concluded, what the degrees or divisions of 

 the said instruments did mean; neither were they ever otherwise graduated, 

 but by standards kept by each particular workman, without any agreement with, 

 or reference to one another; so that whatever observations any curious person 

 mjiy make by his thermometer, to denote the degree of heat in the air, cannot 

 be understood, unless by those who have also thermometers of the same make 

 and adjustment. Much less has the way been shown how to make this instru- 



