192 BRIDGMAN. 



Commercial drawn rod, unannealed, 



At 30° ^- = - 10- 7 (7.32 - 2.7 X lO- 5 ^) p 



I 



o 



At 75° ^- = - 10- 7 (7.39 - 2.7 X 10-*p) p , 



I 



o 



Same commercial rod, annealed, 



At 30° ^- = - 10- 7 (7.29 - 2.7 X 10- 5 ^) p 



\ 



i) 



At 75° % = - 10- 7 (7.37 - 2.7 X KHp) p. 



I 



o 



Pure copper, At 30° %- = - 10~ 7 (7.19 - 2.6 X lO- 5 ^) p 



I 



o 



At 75° %■ = - 10- 7 (7.34 - 2.7 X ICHp) p. 



r> 







Richards has found the initial compressibility at 20° to be 7.4 X 10 -7 . 

 A. W. J. could find no departure from linearity. Correcting their 

 results for the new value for iron, their average compressibility to 

 10000 was 7.1 X 10- 7 , against 6.84 X 10- 7 given by the formula above 

 for pure copper. 



Uranium. I am indebted for this to the kindness of Dr. A. W. Hull 

 of the General Electric Company. It was furnished in the form of 

 rolled strip 0.05 cm. thick, 0.6 cm. wide, and 5 cm. long. I have no 

 chemical analysis. The temperature coefficient of the electrical 

 resistance between 0° and 100° was 0.0022. Because there are no 

 other measurements at present on the electrical properties of uranium, 

 this does not mean much as to the purity, except that probably the 

 purity was not high, but if in the future the properties of pure uranium 

 are measured, this coefficient should give more definite information. 

 This sample was mounted as a tension specimen in the lever apparatus 

 for long specimens. 



The usual two runs were made, at 30° and 75°. The average 

 arithmetical departure from a smooth curve of all 28 points (no dis- 

 cards) was 1.0% of the maximum pressure effect. The average 

 deviation at 75° was two or three times as great as at 30°. The 

 maximum departure from linearity was 0.59% of the maximum pres- 

 sure effect. It is therefore evident that the accuracy of the departure 



