2$ DR. Irvine's and dr. black's 



fame time a quantity of heat added to it to make the whole 

 heat in proportion to its new capacity, furely that body would 



and this is the continue exaflly at the fame thermometrical point. Now 

 e wi jcc. ,j^e!ting ice is that body ; the 1 l-O" are demanded by new capa- 

 city, — would have been more it its capacity had been greater, 



hence. Sec. as and lefs if lefs. On the very principles therefore in diipute, 



before. j^^ ^j^ becoming water ought to receive a quantity of heat, 



and that quantity is not governed by the proportion of 9 to 10, 

 but the whole heats are in that proportion, and the J 4-0° is 

 only their difference. For all calculations on tlje alteration of 

 temperature to be produced by a given portion of heat on a 

 body, from the knowledge of the relation of its capacity to 

 another, and of the number of degrees that other is railed by 

 the fame quantity, continue jufi: only while the capacities con- 

 tinue in the fame proportion. 



The caufe of Surely it is poffible to form a notion that heat (140°,) may 



fluidity afcnbed ^^^^^^ j^^j.^ water as the very caufe of fufion, fo as to alter its 



to coe lame -' ' 



afriwn of heat ftate and change its capacity ; that very heat making the quan- 



>vhlcb enlarges jum due to the new capacity. It is the fad, that ice at 32'* 



the capacities of ... 



bodies. cannot bear the fmallell addition of heat in that Hate, but im- 



mediately begins to be converted into water. Let a quantity 

 much lefs than reprefented by 140°, enter a given portion of 

 ice, fay | a degree. A fmall portion of the ice becomes 

 water; its capacity being increafed as 9 : 10, and here the 

 procefs flops; the entire mafs of ice and water remaining at 

 32**. More heat would alter the ftate and enlarge the capa- 

 city of more of the ice, without raifing its temperature; that 

 is to fay, would fu("e it. How this is done, or in other words, 

 •what it is that happens among the particles may not be eafy 

 to explain or to imagine ; but in my apprehenfion this hypo- 

 thetical part of the dilcufiion would be at leaft as obfcure in the 

 dodrine of latent or combined heat, as in that which afcribes 

 the difappearance of heat during fufions to the enlargement of 

 capacity. 



Thccxperi- As to the difagreement of refults in the hands of different 



philofophers concerning the natural zero, it is to be obferved, 

 that it is one thing fo determine whether bodies have different 



jjve the fame capacities for heat, and another to exprefs thefe by accurate 



tSmTztZ '^' "i^^nbers. There can be no doubt of the fad that bodies have 

 different capacities, and Dr. Irvine's theorem may enuntiate 

 itfelf generally, by faying, that as the capacity of the folid is 



ta 



sntnts on heaC 

 a^-t; mofily too 

 inaccurate to 



