294 ILLINOIS STATE ACADEMY OF SCIENCE 



to indicate that the value of the vapor pressure of mer- 

 cury over a range in temperature from 0'' to 40 °C is near 

 that of the results given by Morley, van der Plaatz, and 

 by the present method, and from the standpoint of ac- 

 curacy of observations, the present values obtained by the 

 present method should be the more accurate. 



The mean values of mercury vapor pressure as read from 

 the mean curve at 10^ intervals are : 



0° 00035 mm. 



10° 000775 



20° 00182 



30° 00407 



40° 008 



Physics Laboratory, University of Illinois 

 April, 1921. 



