302 



BKIDGMAN. 



The behavior under pressure is in many respects Hke that of cad- 

 mium. Zinc evidently is in a state of unstable internal equilibrium 

 as shown by unsteadiness and irregularity of reading, and hysteresis. 

 The hysteresis was not as marked as that of cadmium, however, and 

 the permanent changes of zero were comparatively small, rising at 

 the maximum to 1.2% of the total effect. Five runs were made, 



Temperature 



Zinc 

 Figure 10. Zinc. Thermal E.M.F. of a couple composed of one branch 

 of uncompressed metal, the other compressed to the pressure in kg./cm.^ 

 indicated on the curves, the junctions being at 0°C and the temperature 

 plotted as abscissae. 



at 25°, 50°, 75°, 95°, and 25° again. The last run at 25° was made 

 to find whether any permanent change had been produced by the many 

 changes of pressure and temperature, but there was none, the last run 

 at 25° giving the same average deflection and also the same hysteresis 

 as the first run. In order to reduce to a minimum uncertainties from 

 changing internal equilibrium, two applications of the maximum 



