144. A. E. Bostwick—Electrical Resistance of Metals. 
Long exposures—(method II). 
AandB Mean effect on plate lighted—decrease of 0014 per cent. 
f “ce ‘ “ “ 
A’ and B increase of ‘0053 
Mean effect of lighting plate. Of darkening. 
C increase 004 per cent increase 0046 per cent. 
D diminution °008 es - diminution °014 6 
E increase ‘005 ‘* increase 00 - 
It will be seen that the above results agree with those of 
Siemens and Hansemann rather than those of Bornstein. The 
latter’s objections to Siemens and Hansemann’s methods have 
already been mentioned. The first, that the experiments were 
made on the plate when the circuit though it was closed, apply 
of course also to method I of the series just described. In 
Bérnstein’s experiments by the damping method however, his 
plates were traversed by a current, though of course a very 
feeble one, and it is difficult to see how the difference between 
a diminution of five per cent and no perceptible effect can be 
ai 
Be antes 
accounted for by the fact that the current in one case Was — 
intermittent and in the other constant 
Ornstein’ 
osure is worthy of more attention. The exposures of 
cups, and common binding screws were used. 
t may also be here mentioned that the effect whose ex! 
tence is to be proved or disproved is of course the differenc® . 
between the effects of the light and the heat of the luminous © 
3 
. +4 
aS ees 
ye 
aes 
s second objection relating to the length of the : 
