118 
Mr Patterson, On the effect of a magnetic field 
On the effect of a magnetic field on the resistance of thin 
metallic films. By J. Patterson, B.A., Toronto, 1851 Exhibition 
Scholar. (Communicated by Professor Thomson.) 
[Read 4 March 1901.] 
A. C. Longden in the Physical Review, xi. 2. 40, described a 
method of making standard high resistances from thin films of 
metals deposited on glass by means of the kathode discharge. He 
has shewn that the resistance of these films is much greater than 
that calculated from the ordinary specific resistance of the metal. 
It would be of interest to try what effect a magnetic field would 
have on the resistance of a thin film deposited in this manner 
from a bismuth kathode. 
The apparatus for making the films was the same as that used 
by Longden. To secure good contact between the film and the 
electrodes, the ends of the glass plates were silvered in a silvering 
solution and fine copper wire was wound round the silvered ends ; 
then copper was deposited electrolytically on the wire and on part 
of the silver. The bismuth film was deposited on the glass plate 
thus prepared. 
The films were examined under the microscope to see if there 
was any visible discontinuity, but none could be detected, and as 
there were no interference fringes produced by the reflected or 
transmitted light the films were continuous to the order of the 
wave-length of light. They were also tested by removing half 
the width of the film, the resistance was then doubled, shewing 
that the contacts with the electrodes were good and that, if there 
were any discontinuities in parts of the film, they were equally 
distributed. 
The thickness of the films was measured by Wiener’s method 
( Wied . Ann. 31. 629) and the measurements are correct to 15 per 
cent. 
The resistance was measured by the ordinary Wheatstone 
bridge and a D’Arsonval galvanometer, which had a resistance of 
100 ohms and gave a deflection of 1 mm. on the scale for 2 x 10 -9 
ampere. 
