250 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



diagrammatically the general tendency of the results. The formula 

 actually does not give results better than ^ per cent beyond the 

 range 0° to 50°. The temperature coefficient found above is nearly 

 ten times de Forest Palmer's value, who, however, worked only at 

 the extremes of a wider temperature range than that used here, namely, 

 9° to 100°. 



TABLE IX. 



Variation of Mercury Resistance with Pressure 

 and Temperature. 



No theoretical discussion of the way in which these curves might 

 be expected to behave has been attempted. Only a few points require 

 remark. For instance, it is obvious from the table that temperature 

 has a greater effect on the pressure coefficient of resistance than it 

 does on the resistance itself. The temperature coefficient of the 

 former is 0.00137, and of the latter 0.000888. In other respects the 

 curves behave as one would expect, i. e., at higher pressures the pro- 



