OP ARTS AND SCIENCES. 



41 



Corrected in this way we have, — 



Joule's value 



Reduction to air thermometer 



" latitude of Baltimore 



Correction for sp. ht. of copper 



My value 

 Difference 



427.0 

 427.7 



42G.1 

 427.1 



.7 



1.0 



or 1 in 600 and 1 in 426 respectively. 



But it is evident that all the other temperatures used in the experi- 

 ment must also be corrected, and I have done this in the following 

 manner. The principal other correction required is in the capacity of 

 the calorimeter, and this amounts to considerable in the experiments 

 on mercury and cast-iron, where no water is used. Dr. Joule informs 

 me that the thermometer with which he compared mine was made in 

 1844, but does not give any mark by which to designate it, although 

 it is evidently the thermometer called "A" by him. I shall com- 

 mence with the experiments of 1847. The calorimeter was composed 

 of the following substances, whose capacities I recompute according 

 to what in my paper I have considered the most probable specific 

 heats. 



