670 Prof. J. Patterson on the Electrical 



Table IX. — Resistance of Silver Films. 



Treatment of film. 



Resistance of 

 film. 



Resistance 

 per cm. square. 



Initial resistance of No. 1 



0-3766 



0-3875 



0-2533 

 0-2530 



0-2828 



03240 



0157 



01163 

 01169 



Heatect in vacuo 30 hours to 85° C. ... 

 No. 2 initial resistance 



Alter 4 days without being heated 



No. 3 initial resistance 



Heated in vacuo with electric current 1 

 for 4£ hours with - 5 ampere, and 2 I 

 hours with 0'7 ampere J 





the first two that heating had very little effect on the 

 resistance except that it increased the resistance when heated 

 by the electric current. 



The thickness of these films was also measured roughly, 

 and show ed that their specific resistance would be the same as 

 that obtained by Vincent*, namely, 2'4x 10 — 6 ohms per cm. 

 cube. These experiments were not pursued further. 



The Change of Resistance of the Films produced by a 

 Magnetic Field. 



The change of resistance produced by a magnetic field on 

 a few films was also measured. The apparatus was the same 

 as that used by the author f in the experiments on the change 

 of the electrical resistance of metals when placed in a mag- 

 netic field. The method is briefly as follows : — Three other 

 resistances nearly equal to the resistance of the film were 

 made, and the four connected in the form of the Wheat- 

 stone-bridge. The bridge was balanced by placing one of 

 the arms in multiple arc with a variable resistance. A very 

 sensitive D'Arsoiival galvanometer was used. The films of 

 bismuth and platinum were made by sputtering from the 

 cathode in vacuo, while the silver films were deposited 

 chemically from Common's silvering solution. 



The resistance of the silver films was increased by slotting 

 them, as shown in fig. 12. 



The platinum films were heated in vacuo until their resistance 

 became constant. They were treated exactly like the films 

 whose resistances were measured. Their thickness was not 

 measured, but they were thick films. The results for the 



* Annates de Chimie et de Physique [7] tome xix. p. 494 (1900). 

 t Phil. Mag. June 1902. 



