592 



BRIDGMAN. 



points in Figure 6. Except for one point due to viscosity at 0°, the 

 maximum departure of any reading from the smooth curve was 0.6% 

 of the total pressure effect, and the average numerical departure, 

 including every point, was 0.05%. A preliminary sample gave a 

 few readings at 75° agreeing within the limits of sensitiveness with 



I .007 



(0 



u 



^ .OOi 



I .005, 



0° 20'^ 



40° 60° 80° 

 Temperature 



20° 40° 60° 80° 

 Temperature 



00° 



Cadmium 



2 4 6 8 10 



Pressure, Kg. /Cm.' X 10' 



12 



Figure 6. Cadmium, results for the measured resistance. The deviations 

 from linearity are given as fractions of the resistance at kg. and 0°C. The 

 pressure coefficient is the average coefficient between and 12000 kg. 



those finally obtained. Measurements on this preliminary sample 

 were terminated by leak due to a defective cylinder. The deviations 

 from linearity are very nearly, but not quite, symmetrical and para- 

 bolic. The deviation curves are also reproduced in Figure 6. 



The average temperature coefficient between 0° and 100° at kg. 

 found above is 0.00424. This may be compared with values of Jaeger 

 and Diesselhorst ^ for cadmium from the same source, showing by 

 analysis less than 0.05% of Pb, Zn, or Fe. Their value for cadmium 

 rod is .00421, and for wire 0.00396. (I have corrected both of their 

 data by a factor of 1% to compensate for the difference of range.) 

 The cadmium used above is therefore probably a little purer than that 

 of Jaeger and Diesselhorst. Beckman ®* found 0.00425 for the aver- 

 age coefficient of the cadmium on which he made pressure measure- 

 ments. The initial pressure coefficient at 0° has been found by 

 Beckman to be —0.0592, against — O.O4IO63 above. My average 

 coefficient between 1 and 12000 kg. is — O.O5894 and is in much better 

 agreement with Beckman's initial value. Beckman found a variation 

 of the coefficient of 1.7% over 2700 kg. 



The general character of the results is somewhat different from those 

 of the three previous metals. When the pressure-resistance curves 



