88 Mr. "W. Sutherland on the Law of Attraction 



In passing from the value ofpv—p'v* to the cooling effect 



iL — y , which corresponds to it, account has been taken of 



the variation of s, the specific heat of C0 2 , with temperature. 

 E. Wiedemann's determinations (-1952 at 0° C./2169 at 100°, 

 •2837 at 200°) were adopted, the values at intermediate tem- 

 peratures being obtained by interpolation. On reverting to 

 the theoretical conclusion, it will be seen that the cooling is 



to be proportional to T ; and as s varies with the temperature^ 



it will be necessary to test the theory by seeing whether the 

 product T0s (for the constant value 100 inches of mercury 

 for j?— p f ) is constant. 



In the first of the following tables the total actual cooling 

 effects are Thomson and Joule's experimental numbers (Phil. 

 Trans. 1862) ; in the second the calculated total cooling effects 

 were obtained by them on the supposition that the cooling 

 effects were inversely proportional to the square of the absolute 

 temperature. 



C0 9 . 



Absolute 



temperature, 



T. 



Actual total 

 cooling effect. 



Cooling effect, 

 pv—p'v' 

 Js ' 



Difference of 



the two cooling 



effects, 9. 



Product, 

 T6s. 



273-0 



o 

 4-64 



o 

 1-43 



o 

 3-21 



171 



3086 



3-41 



104 



2-37 



148 



3270 



2-95 



•89 



20 



141 



370-5 



2-14 



•63 



1-51 



120 



Absolute 



temperature, 



T. 



Calculated 



total cooling 



effect. 



Cooling effect, 



pv—p'v' 



Js 



Difference of 



tbe two cooling 



effects, 0. 



Product, 

 T0s. 



2730 

 308-6 

 3270 

 370-5 



4-64 

 5-63 

 3-23 

 2-52 



o 



1-43 



104 

 •89 

 •63 



321 



2-59 

 2-34 

 1-89 



171 

 162 

 158 

 152 



In the first of the above tables for C0 2 , the products TOs 

 show decided enough departure from constancy ; in fact T 2 0s 

 would be nearly constant. The departure may be taken as 

 showing the great value which similar experiments conducted 

 on vapours compressed nearer and nearer to liquefaction and 



