PRESSURE ON RESISTANCE OF METALS. 



595 



the deviation curves is — O.O4I44. The agreement of these vakies 

 is better than in the majority of cases. 



The general character of the results is normal. When the resist- 

 ance-pressure curves for the different temperatures are scaled to the 

 same initial resistance, the curves for the higher temperatures are 

 steeper and are slightly more curved. 



Zinc. This was Kahlbaum's grade "K." Spectroscopic analysis 

 by Mr. A. E. Becker showed traces of cadmium, iron and lead. It 

 was extruded hot into wire of 0.006 inch diameter and wound loosely 

 on a bone core. Connections were made with ordinary soft solder. 

 The initial resistance at 0° was 10.3 ohms. It was seasoned by several 

 exposures to 120° at atmospheric pressure, and by three preliminary 

 applications of 12000 kg. at 100°. A second sample of the same wire 

 was used for the points at 0° and 25°. This was seasoned by subject- 

 ing to 120° and to 12000 kg. at room temperature. 



The smoothed values are shown in Table" VI and the experimental 



TABLE VI. 

 Zinc. 



values in Figure 8. The maximum departure of any point from a 

 smooth curve was 0.9% of the total pressure effect, and the average 

 numerical departure was 0.3%. These results are somewhat less 

 regular than usual. Without making a bone core of new design it 

 was not feasible to use a length great enough for the best results. 

 Within the limits of error the deviations from linearity are sym- 

 metrical and parabolic. 



