184 THOMSON ON CARNOT'S 



by Carnot/s result deduced from experiments on 

 air, is not to be wondered at when we consider the 

 very uncertain nature of his data. 



45. The fact of the gradual decrease of /* 

 through a very extensive range of temperature, 

 being indicated both by Kegnault's continuous 

 series of experiments and by the very varied ex- 

 periment on different media, and in different 

 branches of Physical Science, must be considered 

 as a striking verification of the theory. 



II. On the Heat developed ~by the Compression of 

 Air. 



46. Let a mass of air, occupying initially a 

 given volume V, under a pressure P, at a tem- 

 perature t, be compressed to a less volume F', 

 and allowed to part with heat until it sinks to its 

 primitive temperature t. The quantity of heat 

 which is evolved maybe determined, according to 

 Carnot's theory, when the particular value of //, 



engaged in completing some researches, from which we 

 may expect, possibly before the end of the present year, 

 to be furnished with all the data for five or six different 

 liquids which we possess at present for water. It is there- 

 fore to be hoped that, before long, a most important test of 

 the validity of Carnot's theory will be afforded. 



