4:34 Mr. G. H. Livens on the Electron 



water of Lake Ontario, the conductivity of air when 

 measured on the surface of that lake has been found to 

 be represented by 2' 6 ions per c.c. per second, which is 

 the lowest conductivity hitherto observed for air. 



4. Reasons have been adduced which support the view 

 that air has no electrical conductivity apart from that 

 impressed upon it by radiations traversing it which are 

 emitted by the walls of the containing vessel, and by the 

 land, the atmosphere, and the water in the neighbourhood 

 of the enclosed air whose conductivity is being measured. 



We desire here to acknowledge the services of Mr. P.. 

 Blackman, Mr. T. Plaskett, and other members of the 

 Mechanical Staff in the Physical Laboratory for assistance 

 in carrying out the investigations under rather trying 

 conditions. 



The Physical Laboratory, 

 University of Toronto, 

 May 1st, 1915. 



XLV. On the Electron Theory of the Optical Properties 

 of Metals.— II. By G. H. Livens*. 



1. Introduction. 



IN a previous paper a complete discussion of the electron 

 theory of the optical properties of metals was given on 

 the basis of the statistical theory of the motion of the elec- 

 trons in metals, originated by Drude and Thomson, but on 

 the simplifying assumptions, also used by these authors and 

 Lorentz, that the electrons and atoms merely interact on one 

 another in collision like elastic spheres. It has subsequently 

 been found possible to give the theory a much greater 

 degree of generality by adopting the more probable notion 

 that the atoms are spherical repelling or attracting centres 

 of force. 



The main results of the present paper with certain modi- 

 fications have already been obtained by Bohr, Enskog t, and 

 apparently also by Ishiwara, but by methods hardly so simple 

 or direct as the form of the final results might suggest. Some 

 advantage may therefore be gained by deducing them again 

 from the simpler analytical formulation of the theory sug- 

 gested by the present writer, and including in addition the 



* Communicated by the Author. 



t Ann. der Physik, xxxviii. p. 731 (1912), where the reference to. 

 Bohr's and Ishiwara's dissertations will be found. 



