172 BRIDGMAN. 



Summary. 



By the employment of a new method, by which the resistance is 

 measured simultaneously for a heavy direct current and a small super- 

 posed alternating current of acoustical frequency, deviations from 

 Ohm's law at high current densities have been detected and measured 

 in leaf gold and silver. The maximum current densities were about 

 5 X 10^ amp/cm^, and the deviations from Ohm's law were of the 

 order of one per cent. If the mechanism of conduction is a free path 

 mechanism, these results probably mean that the free path is much 

 longer than supposed on the classical electron theory. 



It is a pleasure to acknowledge my indebtedness to my assistant 

 Mr. J. C. Slater for making nearly all the readings. 



1 J. J. Thomson, The Corpuscular Theory of Matter, 1907, p. 55. 



2 Clerk Maxwell, J. D. Everett, A. Schuster, Brit. Assoc. Rep. 1876, 36-63. 



3 F. Wanner, Phys. Rev. (2) 15, 531-532, 1920. 



4 E. Lecher, Sitzber. Wien. Akad. lie^^^ 1, 49-60, 1907. 



5 H. R. von Traubenberg, Phvs. ZS. 18, 75-78, 1917. 



6 J. Patterson, Phil. Mag. 4, 652-678, 1902. 



7 W. F. G. Swann, Phil. Mag. 28, 467-496, 1914. 



8 P. W. Bridgman, Phys. Rev. 9, 269-289, 1917, and 17, 161-194, 1921. 



The Jefferson Physical Laboratory, 

 Harvard University, Cambridge, Mass. 



