122 MOLECULAR MOTION AND ITS ENERGY 55 



to a certain extent. For, since K, as a part of JEZ", is not 

 greater than H, but can at most be equal to H, our formula, 

 which can be put in the form 



C 2tf 



e ^3H' 

 or, more generally, 



=1 2 K - K, 



c = 3 H - H Q ' 



gives limits for the values which the ratio of the two 

 specific heats can have ; thus the formula gives 



or the value of the ratio must in all cases lie between 

 1 and f . 



Since the experimental determinations of this ratio 

 mentioned further on confirm this theoretically deduced law 

 without exception, we may consider ourselves justified in 

 using the formula 



K_ 3C-c 

 H = 2 c 



in the reverse way, and in calculating for different gases 

 the ratio of the kinetic energy K of the molecules to the 

 whole heat-energy H from the values of the ratio of the two 

 specific heats that have been determined by observation. 

 At least, for a gas whose specific heat is not variable with 

 the temperature the sufficiency of this formula instead of 

 the more general one 



K - K Q __ 3 C-c 



H - H Q ~ 2 c 



will not be contested ; for other gases the simpler formula 

 will give values that are very approximately correct. 



The value of the ratio in which the two specific heats 

 stand to each other has indeed been experimentally deter- 

 mined for a tolerably large number of gases, though un- 

 fortunately not in all cases with such certainty as for our 

 purpose is desirable. For since the formula does not con- 

 tain only the ratio, but also the difference of these magni- 



