448 Mr. Herapath on True Temperature, and the [Dec. 



expressed in terms of the weight, baromerin, and temperature 

 of the body itself, by only changing the weight and baromerin 

 of the water for the like things of the body. Thus if the weight 

 of the body be Q, and its baromerin q, that of water being 22, 



we shall have W" = Q q — ^ 



1000 



o 



3000 



Cor. 2. — Hence conversely the baromerin of any body may be 

 discovered by the weight of ice it will melt in the calorimeter. 



For by the last Cor. we get q = iooo i' wmcn ' s a general 



expression. 



Scholium. 



Because by " specific caloric " is meant the ability of bodies 

 to affect the temperature of another under equal circumstances, 

 reckoning in Fahrenheit degrees with our English philosophers ; 

 and because these degrees within ordinary limits are sensibly 

 proportional to our units of true temperature, it is plain that the 

 ratio of our baromerins, determined from the preceding theory, 

 ought to coincide very nearly with the ratio of the "specific calo- 

 rics." Let us see by the calculation of one of Lavoisier and 

 Laplace's experiments how far this will be the case. They put 

 a piece of iron-plate, at the temperature of 97-5° centigrade, 

 weighing 3-77264 kilogrammes into the calorimeter, and at the 

 end of 1 1 hours found its temperature was reduced to 0° cent, 

 and that '542004 kilogrammes of ice were melted. By the 

 tables, p. 515, vol. i. Murray's Chemistry, 97-5° cent. = 207-5 

 Fahr. = 1168-6 true temperature. Therefore, t = 1168-6, W' = 

 •542004, and Q = 3-77264 ; whence by Cor. 2, of this Prop. 



q = * = 2-55635 the baromerin of iron plate ; the 



baromerin of water being 22. Dividing the baromerin thus 

 found by 22, it gives '116189 for the baromerin of iron plate, that 

 of water being 1. MM. Lavoisier and Laplace calculated the 

 "specific caloric" of this body for the same unity at -11051, 

 which very nearly coincides with our baromerin. A like accord- 

 ance would, I have no doubt, be found in other cases, but at 

 present this must suffice. 



Prop. XIX. Theoe. XV. 



In a former part of this paper I have shown that water may be 

 cooled belowthe temperature of its liquefaction without, solidifying, 

 but that on agitating it, a part becomes frozen, and the tempera- 

 ture of the whole rises to 1000. Let 10 be the weight of a given 

 quantity of water cooled down to t, and let it be shaken ; then 



the weight of the quantity frozen will be equal to 30Q0 — 22 w. 



Put W to denote the weight of the water frozen, and we shall 



