OP ARTS AND SCIENCES. 131 



My only object was to confirm by this method tbe results deduced 

 from the experiments on the mechanical equivalent; and this I have 

 done, for the experiments nearly all show that the specific heat of 

 water decreases to about 30°, after which it increases. But the 

 mechanical equivalent experiments give by far the most accurate 

 solution of the problem ; and, indeed, give it with an accuracy hitherto 

 unattempted in experiments of this nature. 



But whether water increases or decreases in specific heat from 0° to 

 30° depends upon the determination of the reduction to the air ther- 

 mometer. According to the mercurial thermometers Nos. Gl (>•'), G1G.3, 

 and GIGG, treating them only as mercurial thermometers, the specific heat 

 of water up to 30° is nearly constant, but by the air thermometer, or by 

 the Kew standard or Fastre, it decreases. 



Full and complete tables of comparison are published, and from 

 them any one can satisfy himself of the facts in the case. 



I am myself satisfied that I have obtained a very near approxi- 

 mation to absolute temperatures, and accept them as the standard. 

 And by this standard the specific heat of water undoubtedly decreases 

 from 0° to about 30°. 



To show that I have not arrived at this result rashly, I may men- 

 tion that I fought against a conclusion so much at variance with my 

 preconceived notions, but was forced at last to accept it, after studying 

 it for more than a year, and making frequent comparisons of ther- 

 mometers, and examinations of all other sources of error. 



However remarkable this fact may be, being the first instance of 

 the decrease of the specific heat with rise of temperature, it is no 

 more remarkable than the contraction of water to 4°. Indeed, in 

 both cases the water hardly seems to have recovered from freezing. 

 The specific heat of melting ice is infinite. Why is it necessary that 

 the specific heat should instantly fall, and then recover as the tempera- 

 ture rises ? Is it not more natural to suppose that it continues to fall 

 even after the ice is melted, and then to rise again as the specific heat 

 approaches infinity at the boiling point? And of all the bodies which 

 we should select as probably exhibiting this property, water is cer- 

 tainly the first. 



(&.) Heat Capacity of Calorimeter. 



During the construction of the calorimeter, pieces of all the material 

 were saved in order to obtain the specific heat. The calorimeter which 

 Joule used was put together with screws, and with little or no solder. 

 But in my calorimeter it was necessary to use solder, as it was of a 



