BURGESS AND KELLBERG: ALLOTROPY OF COPPER 



661 



few seconds, often as close together as 0.03°C. The copper was 

 examined microscopically by Mr. Rawdon and showed a small 

 quantity only of cuprous oxide inclusions, see figure 2. 



In Table II is given a list of 

 the ranges over which observa- 

 tions were taken, together with 

 the mean rate of heating or 



cooling. Several series were \ 



taken in the range 60-70° by 

 the second method, as there 



were apparent indications, from . ', 



the observations by the first 

 method, of a possible resistance 

 effect. This was, however, at- 

 tributed to convection since it 

 was not constant in position and 

 could be introduced at will by 

 opening a window or door in the 

 laboratory. In the second and third methods no anomaly could 

 be detected, to at least 1 part in 50,000. The last series taken 



Fig. 2. Photomicrograph of longi- 

 tudinal section of copper wire. 



~t 



6 

 c 

 o 

 c 



1- 

 111 



§: 







o 



It 



I"- 



Te mperature 



\b5' [66' 167' 





.3-2 - 1 ■( -2 -J 



Hesisfance afP/atinuminOhms 



Fig. 3. Resistance of copper vs. platinum and plot of residuals. 



