1891 - 92 .] Prof. Tait on the Kinetic Theory of Gases. 35 
The difference, P-Q, is (when multiplied, as above by 12‘2) 
nearly equal to the excess of the heat required to raise the tem- 
perature of the liquid (at constant volume) to the critical point, 
over that required to raise the temperature of the vapour, from 
saturation, through the same range, the volume remaining un- 
altered. 
It appears that CO 2 , when passing through the range of volume,, 
spoken of in § 69 of Part IV. of my paper, has about half the 
density of water. 
