236 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



first part of this paper. The steel parts of this gauge may of course 

 show hysteresis, but if we assume that the liquid transmitting the 

 pressure shows no hysteresis, which is almost certainly true, it is 

 evident that any hysteresis effects in the steel parts will merely affect 

 the correction for distortion of the gauge. The largest value of this 



TABLE II. 



Comparison op Mercury Gauge against Absolute Gauge at 

 Increasing and Decreasing Pressures, to show Freedom 



from Hysteresis. 



is about T V P er eent. Within the limits of error, therefore, the abso- 

 lute gauge shows no hysteresis. Freedom of the mercury from hys- 

 teresis will be shown by agreement of the resistance measurements 

 under increasing and decreasing pressure. 



Comparisons of mercury resistance and absolute gauge were car- 

 ried out with one mercury resistance (R 9) of soft Jena glass tubing 

 No. 3880 a, and two absolute gauges, as has already been mentioned 

 in the first part of this paper. The results of one of the comparisons 



