286 H. A. Rowland—Absolute Unit of Electrical Resistance. 
when @ is small, and this, in one or two of their experiments, 
exceeds unity or a exceeds 28°°6, which is absurd. Taking 
: R ; 
even one of the ordinary cases where —‘=1'02 and + is about 
zo, We a=12° nearly, which is a value so large that it 
would surely have been noticed. e may conclude 
that no reasonable amount of torsion in the silk fiber could 
these currents, but has failed to consider the theory of them. 
Now, from the fact that after any number of revolutions the 
number of lines of force passing through any part of the appa- 
ratus is the same as before, we immediately deduce the fact 
that, if Ohm’s law be correct, the algebraical sum of the cur- 
rents at every point in the frame is zero, and hence the average 
magnetic action on the needle zero. But although these cur- 
rotation, the effect is nearly but not quite eliminated. The 
amount of the effect is evidently dependent upon the velocity 
of rotation and increases with it in some unknown proportion, 
and the residual effect is evidently in the direction of making 
the action on the needle too small and thus of increasing R. 
- these currents are the cause of the different values of R 
a ta with positive and negative rotation, we should find 
at if we picked out those experiments in which this difference 
was the greatest, they should give a larger value of R than the 
others. Taking the mean of all the results} in which this dif- 
Reports on Electrical egrysa London, 1873, p. 191. 
and hare thong probate that te ae tre Sein Sl nt i a 
column should read 1:0032 and 1-0065 instead of 1:0040 and ‘9981, and in my 
discussion I have considered them to read thus. i ii 
