158 BELL SYSTEM TECHNICAL JOURNAL 



more frequent occurrence in the future. Among such possible inno- 

 vations he mentions a better conductor of electricity, a cable covering 

 superior to the present lead alloys, higher grade insulation, and a 

 contact material less subject to corroding and freezing. The recent 

 advances made in metallic alloys give every promise of a more brilliant 

 future. 



The Thickness of Spontaneously Deposited Photoelectrically Active 

 Rubidium Films, Measured Optically} H. E. Ives and A. L. Johns- 

 RUD. Measurements of the phase shift on reflection of polarized light 

 from a reflecting surface on which there is deposited a very thin film 

 of metal are described. The materials were the thin films of rubidium 

 which are slowly deposited on glass or platinum when these have been 

 thoroughly out-gassed. The apparatus was so arranged that measure- 

 ments of the photo-electric activity could be made simultaneously with 

 determinations of the optical effect due to the thin film. The data 

 were then interpreted in terms of the electromagnetic theory of light 

 using special developments due to T. C. Fry, to be published in the 

 Journal of the Optical Society for January, 1928. 



It is concluded from the measurements that the film of rubidium 

 deposited on glass after fourteen days is of the order of magnitude of 

 one atom thick. The theoretical effect of a layer of rubidium on 

 platinum of the order of even several atoms thick is, however, so 

 small as to lie within the errors of observation. "It thus appears, 

 if the validity of the optical measurements of thickness is conceded, 

 that the photo-electric emission is obtained when a layer of rubidium 

 of approximately one atom in thickness is present," they conclude. 



3 Opt. Soc. Amer. Jl., Vol. 15, 374, December, 1927. 



