Prof. Callan on the Induction Apparatus. 339 
I have shown that the effect of the condenser is at least to 
increase the rapidity with which the core loses its magnetism, and 
probably to increase its magnetic power. Hence my explanation 
of the action of the condenser is confirmed by the effect of the 
condenser on the currents produced in each section of the core. 
The principle of this explanation of the action of the condenser 
suggested to me a new form of condenser, which I expected 
would act more powerfully than the condenser now in use. The 
new condenser was to consist, not of sheets of tinfoil, but of a 
large number of very thin sheets of iron, arranged in such a way 
that one-half of them would form one plate, and the other half 
the other plate of the condenser ; and that the electrical current 
by which each plate would be charged, one positively, the other 
negatively, should not enter simultaneously each of the iron. sheets 
forming the positive plate, nor leave simultaneously all the iron 
sheets in the negative one, but should flow through the whole 
length of each sheet, before entering into the next. In order to 
make a condenser of this kind, I got 112 sheets of iron, each 
28 inches long, 10 broad, and about 2,th of an inch thick. I 
intended to arrange them so that the current by which they 
would be charged, at the moment the connexion between the pri- 
mary coil and battery would be broken, should flow successively 
through the whole length of the 112 iron sheets, or through one 
plate equal in length to the sum of their lengths, which exceeds 
250 feet. Had I had time to make, as I intended, our iron con- 
denser in this way, the iron plates would be strongly magnet- 
ized by the electrical current flowing through their entire length; 
and in losing their magnetism, would produce a powerful second- 
ary current, tending to destroy or to reverse the magnetism of 
the core, and thus increase the intensity of the secondary cur- 
rent. In the ordinary condenser there is one electrical current 
tending to destroy the magnetism of the core: in an iron con- 
denser made as I have described, there are two currents tending 
to produce the same effect; viz. the current arismg from the 
rush of electricity from the positive to the negative plate of the 
condenser, and the current caused by the demagnetization of the 
iron plates. In order to save time and trouble, I made our iron 
condenser in the ordinary way. When I have leisure I may 
make it in the manner I have just described. 
The seventh result consists in the discovery of some new facts 
regarding the condenser, which have not been hitherto noticed 
in any publication. First, I have found that the action of 
the condenser is feeble when the core is a solid bar of iron; 
secondly, when it is a coil of fine insulated iron wire not having 
a bundle of iron wire, or a coil of thick covered iron wire in the 
hollow part of it; thirdly, when the quantity of iron in the 
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