~ 
488 W.A. Norton—Force of Effective Molecular Action. 
perature, and must answer to dm, while / remains constant. 
/ 
dm ‘ 
Thus dz’= sfar2? and therefore the ratio becomes 
dm' _dm'_dm 
fee WW in 
For the case in which the volume is constant, while the tem- 
perature rises, 
df= 
Thus the ratio of the increase of volume is equal to the ratio 
of the increase of elastic pressure. We may assume that from 
a certain absolute temperature, T, m increases uniformly for 
each increment, 1° of temperature. Let ¢ denote the actual 
m_ dt ; 
temperature above T; then m=c’d, and gaan & From which 
m! cad df _ dm’ _ dm! _ dm 
ee 
it appears that above T the increase of volume, or of the elastic 
pressure, takes place uniformly ; that is, is equal in amount for 
ual increments of temperature. e may conclude from this 
investigation that Gay Lussac’s law holds good only for that 
range of pressure and temperature within which the law of 
Mariotte is fulfilled; and that it is not strictly true for the 
