ON THE POLARITY OF THE DIAMAGNETIC FORCE. 
245 
is from larger to smaller numbers. This is the opposite result to that obtained when 
the current flowed in the opposite direction ; and it proves that the polarity of the 
bismuth eylinders depends upon the direetion of the current, ehanging as the latter 
changes. It was pleasant to observe the prompt and steady march of the magnet as 
the cylinders were shifted in the helices. When the magnets, operated on by the bars 
of bismuth, were moving in any direction, by bringing the two opposite ends of the 
bismuth bars into aetion, the motion could be promptly ehecked ; the magnets could 
be brought to rest, or their movement converted into one in the opposite direction. 
I may add to the above a series of results obtained some days subsequently in the 
presence of Professors Faraday, De la Rive and Marcet. 
IV. 
Bismuth cylinders. 
Position 1. 670 
Position 2. 650 
Position 3. 630 
The difference between positions 1 and 3 amounts here to forty divisions of the scale ; 
subsequent experience enabled me to make it still greater. 
It was found by experiment, that when the motion was from lower to higher num- 
bers it denoted that the poles NN', fig. 4, were repelled from the spirals, and the poles 
SS' attracted towards them. When, on the contrary, the motion was from larger to 
smaller numbers, it indicated that the poles NN' were attracted and the poles SS' 
repelled. In the position fig. 1, therefore, of Tables III. and IV. the poles NN' were 
repelled by the ends no of the bismuth cylinders, and the poles SS' attracted, while in 
the position fig. 3, the poles NN' were attracted by the ends mp, and the poles SS' 
repelled; the ends n and o, therefore, acted as two north poles, while the ends m 
and JO acted as two south poles. Now the direction of the current in the experiments 
recorded in the two tables referred to was that shown by the arrows in fig. 4. Stand- 
ing in front of the instrument, the direetion in the adjacent face of the spiral H'E' was 
from right to left, while it was from left to right in HE. From this we may infer that 
the polarity of the bismuth cylinders was the reverse of that whieh would be excited 
in cylinders of iron under the same circumstances. The assertion however shall be 
transferred from the domain of deduction to that of fact before we conclude. 
Let us now urge against these experiments all that ever has been urged by the 
opponents of diamagnetic polarity. The bismuth cylinders are metallic conductors, 
and in moving them through the spirals induced currents more or less powerful may 
be excited in these conductors. The motion observed may not, after all, be due to 
diamagnetic polarity, but to the currents thus excited. I reply, that in all cases the 
number set down marks the permawewi position of rest of the magnets. Were the 
action due to induced currents, these currents, being momentary, could only impart 
2 K 
MDCCCLVI. 
