(593 ) 
same for all metals. The rather large deviations from this law have 
led Drvpe to assume more than one kind of free electrons, an hypo- 
thesis we shall have to discuss in a sequel to this paper. For the 
moment I shall only observe that one reason for admitting the 
existence not only of negative but also of positive free electrons 
lies in the fact that the Hani-effect has not in all metals the same 
direction. 
(March 22, 1905). 
