PAPERS ON CHEMISTRY AND PHYSICS 307 



temperature. The carbon film itself lias a rather high 

 negative temperature coefficient of resistance, which is, 

 however, easily measured if necessary. 



The results of this investigation can be confirmed only 

 after a long interval of time, for time is the important 

 test of the constancy of a resistance material. The 

 points in the above report which have not been com- 

 pletely explained are to be investigated more thoroughly 

 at a later date. 



The writer wishes to express his appreciation of the 

 help and criticism of Dr. E. H. Williams under whoso 

 direction this work has been carried on. 



