THEORIES OF HEAT, 27 



ory, that the 140^ entering ice during its change of forms, But it was nut 

 (hould be lefTened in the ratio of 9 : 10, and fliould therefore ^^f^^^ f * 



and therefore 



be 126°, or in other wordsi, if the heat entering the ice were the 126' of 

 only enough to raife the ice ] 40", that the temperature of thereat are con- 



„ , , , n „ . . r r i ,i • r uJered as having 



■water fliould be 158". But it is ealy to lee that on this lup- beyond doubt 



pofition the water would contain two portions of heat, namely, combined 'witb 



its original quantity from the natural zero to 32'', ^^^preflTed ^^'-^^"^^^^^ 



in degrees according to the capacity of ice, and the fuperadded Reply. Dr. 



portion from 32 to 158, exprefled in dep-rees according to that J^^o^P^oni"}^'* 

 ^ , . 1 • r, ftatement of the 



of water. The ice would no doubt according to this ftatement, change of capa- 

 become water without abforbing any heat, and the water city, attends to 

 would be merely heated as in every other cafe. But Dr. Ir- heat only, and 

 vine, and after him Dr. Crawford, and the writers of ele- totally overlooks 

 mentary treatifes for the laft fifteen years, and I believe I may ^^^^^^ iu^the* 

 venture to fay every one of our philofophers, except Dr. Thomp- body, 

 fon himfelf, have flated this docirine of capacities to be, that ^"^'^'"•'^"'''e 

 every one of the thermometrical degrees expreffing the whole j^^.^ irvine and 

 of the heat contained in a body, are to be taken in proportion all writers but 

 to its capacity; and therefore that if the ice fuddenly changed ^^'"^^^nfide'^d 

 its capacity, it would abforb not merely a rateable proportion the ivhoU keat 

 of what heat might be prefented to it, but an abfoiute quan-'" ^ ''"^y ^'* 

 tity to make up for its new capacity. For the heat neceffary rure as thtmea- 

 to raife the temperature of ice each degree from natural zero,/';''^ "/"^ '■^Z"- 

 is (o the heat neceflary to raife water each degree from the 

 fame point as the capacity of tlie one body is to that of the 

 other. Ice cannot then as it acquires its new form, (liew any Ice in fufion 

 augmentation of temperature till the differences between the f-' 'l^'^'*^ 



° "^ bc.t prefented t9 



heats of each degree from the lowefl point be made up. This ic until its en- 

 difference amounts to the HO'^ found by the experiment, and !^'^^^ ^^^P^'^^fy 

 cannot raife the water even the fraflion of a degree in tempe- cannot til'then 

 rature, becaufe it is barely fufhcient for the demands of its^^^^ ^nyincreafa 

 new capacity. Had the 140*^ been applied to water, d,-/*' '^'^P^ature, 

 Thompfon's affertion of the rife of temperature would have 

 been jufi, but it can have no reference whatever to heat ap- 

 plied during a change of capacity. 



The fame arguments are repeated in page 271, and the fame If the capacity 

 miftake reigns through the whole. Is it not obvious, that if°^^ body were 

 you would inflantaneoufly increafe the capacity of any body,c,eafedTts'tem- 

 it would immediately become colder, and its temperature finkperature wjuid 



as much lower as its new capacity was higher. In the fame^^ ' 



•r L J I • • r 1 1 I - /• . or It would con- 



way, it a body has Us capacity luddeniy increafed, and at the t nue f+ationary 



fame '^ ^^^ '^^^' "^^^^ 

 added i 



