178 EF. H. Hali—New Action of Magnetism 
therefore in estimating the thickness of the strip from the elec- 
trical resistance, the effective length of the strip was taken to be 
not 6°05 cm., but 88cm. Assuming the specific resistance of 
the silver in this plate to be 00000165 ohms, the value given 
by Jenkin for “hard drawn” silver, we obtain as the thick- 
ness of the strip ‘00000407 cm. It will be shown below that 
this value is probably very much too small, but I will for the 
moment give the results obtained on the basis of this estimation 
of the thickness. 
assing over a result obtained at quite an early period of 
the experiments, and which there are excellent reasons for re- 
jecting, we have 
Mx V 
M. C. i’ 
Jan. 30th, 7120 ke X tan 43° 38’ 487 * 10” 
. ‘ = Sit 32. 499 x 10"° 
Mean 493 x 10” 
The discrepancy between this result and that obtained with 
the thicker strip of silver was so great, that I determined to try 
Silver Film (B). 
have assumed the thickness of (B) to be the same as that 
h 
I 
of (A). The other dimensions are about the same, and the 
result is 
M x V 
M. C. EK’ 
May 4th, 6640 kX tan 47° 39’ 491 «* 10” 
The agreement of this result with the mean of those just pre- 
ceding is entirely satisfactory, and the discrepancy above men- 
tioned, as existing between the results with plates of different 
kinds, is confirmed. This disagreement was so large as to be 
difficult to account for, without the hypothesis of a specific 
difference exhibited by different forms of the same metal, under 
the conditions of the experiment. To be sure the method of 
estimating the thickness from the electrical resistance was open 
to suspicion. Among other probable sources of error there was 
the possibility of having assumed a wrong value for the spe- 
cific resistance of the silver in this condition. It did not ap- 
pear to me probable that an error of about 400 per cent could 
be accounted for in this way, but it seemed worth while to 
attempt a determination of the thickness of the films*y another 
method. 
Plate (A) was taken and cleaned with aleohol to remove the 
particles of cement adhering to the glass and metal. The 
area of the silver film was roughly determined, and the plate 
was dried and, when cool, carefully weighed. The silver was 
. 
