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platinum and palladium as with antimony and bismuth. But 
they are exhibited with greater force by those metals which 
decidedly show revulsion. Silver and copper discs are so 
strongly drawn within the polar pieces on breaking circuit, 
as frequently to pass out at the other side of the polar pieces. 
As it appeared to me that these transverse motions were, 
to a considerable extent, independent of the other pheno- 
mena of dia-magnetism, it occurred that they were produced 
by secondary electrical currents, induced in the disc of 
metal; and to ascertain whether this could be demonstrated 
experimentally, I took a piece of copper wire, about one- 
fiftieth of an inch in thickness, and folded it so as to make 
a flat spiral of the size of the discs previously employed, 
and of which the folds did not touch each other. On sus- 
pending the insulated spiral between the polar pieces it 
did not exhibit the transverse motions, nor the short and 
quick movement on completing circuit ; or the revulsive 
motions on breaking circuit. But on constructing another 
spiral similar to that before-mentioned in all respects, ex- 
cepting that part of the wire from the centre was prolonged, 
and put into connexion with the other end, forming the 
external fold, the motions, both revulsive and transverse, 
were exhibited in like manner as if a disc had been employed, 
though more feebly, as might be expected, inasmuch as 
any electrical current would have to pass through a con- 
siderable length of wire, and would meet with much greater 
resistance than it would have done in the disc. 
Several discs of copper wire, folded in various manners, 
were tried with the like results; for if the folds were 
insulated, and the ends not in contact, so as to form a 
circuit, revulsive motions were not exhibited; but if the 
two ends were connected, then the revulsive motions, at- 
tractive or repulsive, according to the circumstances, or 
the lateral motions, were exhibited as before-mentioned. 
