Properties of IJiin Metal Films. 



671 



bismuth films were given in a note communicated to the 

 Cambridge Philosophical Society*, and are given here for 

 completeness. The results are given in Table X. 



Fig. 12. 



Table X. — Change of Resistance in Magnetic Field. 



Film. 



Thickness 

 in cm. 



Eesistance. 



Magnetic 

 field. 



5? 10 4 . 



Bismuth . . . 



Platinum ... 

 Silver 



1 X 10-5 



6x10-6 



4X10-6 



... 



58-04 

 10305 

 968-7 



26200 

 27300 

 26200 

 27300 

 26200 

 24400 

 24100 



270 

 31-0 

 53 

 59 

 10 

 0-35 

 10 







Comparing these results with thore obtained by the author f 

 for the change of resistance produced by the magnetic field, 

 it will be seen that in platinum and silver the values are 

 slightly greater for the metal than for the film, but they are 

 of the" same order in both cases. In bismuth films, however, 

 the change is very small compared with the change in the 

 metal, and the magnitude of the change decreases very rapidly 

 with the decrease of thickness. 



Contact-Difference of Potential. 



The contact-difference of potential between the film and 

 the cathode from which it was deposited was measured. The 

 film and cathode were each connected to one pair of quadrants 

 of a quadrant electrometer. All connecting wires were care- 

 fully screened with conductors connected to earth. The film 

 and* cathode were placed about 1 cm. apart, and the air 

 between the plates ionized by Rontgen rays. The electrodes 

 took up the potential-difference in a few seconds, but the rays 

 were left on until the electrometer remained steady. Using the 

 bismuth cathode and a film deposited from it, a contact-differ- 

 ence of potential of 0"034 volt was obtained, the film being 



* Proc. Camb. Phil. Soc. vol. xi. ot. % p. 117. 

 t Phil. Mag. June 1902. 



