382 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



are to be corrected by about 0.4 per cent for the increased initial volume 

 at 22°. The results given in the figure are from smooth curves drawn 

 through the points so determined. The compressibility is less at higher 

 pressures, as it is universally for all liquids, and is greater at higher 

 temperatures, as it is for everything except water. The decrease of 



I 



? 



-< 



LiJ 



.000180 



.000175 

 .000170 



.000105 

 .000100 



.000153 

 .000150 

 .000145 

 .000140 







PRESSURE.KGM/CMXIQ 



6 



3 



FiGUKE 10. The mean dilatation per degree between 0° and 22° for mercury 

 as a function of the pressure. 



compressibility with pressure is very nearly linear, but nevertheless 

 shows a tendency to become more rapid at higher pressures, which is a 

 little surprising. The decrease of compressibility with pressure is more 

 rapid at the higher temperature. Whether the compressibilities at 

 different temperatures would ever become sensibly equal cannot be 

 determined because of the entrance of the solid phase. 



The dilatation of the mercury, or rather the derivative ( — ) , may 



\drjp 



be found from the distance apart of the isothermals at 0"" and 22°. 

 The results are shown in Figure 10. The dilatation becomes less at 

 higher pressures, the rate of decrease also becoming less as one would 

 expect. 



The data so found, ( — ) and f — ) , are sufficient to give the dif- 



ference of the specific heats at ditierent pressures, for we have the 

 relation, 



