PRESSURE ON RESISTANCE OF METALS. 



601 



the same initial resistance, the steepness increases shghtly at the 

 higher temperatures as is normal, but the curvature becomes less at 

 an accelerated rate as temperature increases. The shift of the pres- 

 sure of maximum deviation from linearity to a value above the mean 

 pressure at the higher temperatures is also unusual. 



Gold. The gold, like the silver, was furnished by the United States 

 Mint at Philadelphia in the form of wire 0.06 inches in diameter drawn 

 down through steel dies from bars of "proof" metal in which no 

 impurity whatever could be detected chemically. Dr. Tuttle found 

 that the amount of impurity introduced in the drawing was practically 

 the same in amount as for the silver. I scraped the surface of this 

 wire with glass, just as the silver, reducing the diameter to 0.04 inch. 

 From this size it was drawn to 0.004 inch through diamond dies and 

 covered with single silk by the New England Electrical Works. It was 

 wound into a coreless toroid of 23.5 ohms initial resistance and sea- 

 soned at the same time as the cadmium. Connections were made by 

 silver soldering. 



The smoothed results are collected in Table IX, and the experi- 



TABLE IX. 



Gold. i 



mental values of the average coefficient and maximum deviation 

 from linearity in Figure 11. Kerosene was used as the transmitting 

 medium throughout, and most of the departure from smooth curves 

 is to be attributed to its viscosity. The average zero shift after a 



