24S 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Palmer's value. In view of the magnitude of the variation found in 

 the coefficient over the pressure range, the uncertain correction for 

 the glass introduced by de Forest Palmer, and the magnitude of his 

 probable error, tins agreement is better than could be expected. 



By combining the two empirical formulas for change of specific 

 volume resistance and change of volume of the mercury, the value 

 of resistance times density (R-D), i. e., the specific mass resistance, 



1000 



2000 3000 4000 5000 6000 7000 



Figure 9. The changed resistance of mercury under pressure in terms of 

 the resistance under zero pressure. The curve shows the measured resistance 

 corrected for the distortion of the glass containing vessel. The curve R-D 

 shows the former curve corrected for the changed density of mercury. It 

 shows the pure pressure effect on resistance, that is, the resistance corrected 

 for the increased conductivity due the increased concentration of the mole- 

 cules. The smallness of the change of resistance due to this concentrating of 

 the molecules is to be noticed. 



may be found. The departure of this from constancy may be de- 

 scribed as the pure pressure effect on mercury resistance. In Table 

 VIII the specific volume resistance and the specific volume resistance 

 multiplied by the density are given for various pressures. They are 

 also shown graphically in Figure 9. The curves are similar in all 

 respects and show no indications of any remarkable behavior at 

 higher pressures. The comparatively small part played by the change 

 of density in the total change of resistance under pressure is of interest. 



