324 Prof. Callan on the Induction Apparatus. 
aid of a single galvanic cell,—a coil which is now to be used for 
working the Atlantic Telegraph. Mr. Faraday was the first who 
developed the laws of electrical induction ; but he did not discover 
the method of making a coil by which a current of very great 
intensity may be obtained by means of a very small battery. 
This was first discovered in Maynooth College in 1836. In the 
summer of 1837, I sent the late Mr. Sturgeon a small coil 
which he exhibited at a meeting of the Electrical Society in 
London, and from which he gave shocks to several of the mem- 
bers. After the meeting, I received a letter of thanks from him, 
in which he described the astonishment of those who experienced 
the extraordinary power of the coil. This was the first induc- 
tion coil of great power ever seen outside the College of May- 
nooth. The first notice of the discovery of the coil is found in 
a paper of mine published in the London Philosophical Maga- 
zine for December 1836. In 1836 and 1837 I also discovered 
that the intensity of the current induced in the coil increased 
with the number of cells employed, and that a shock may be got 
from the coil at the moment of making as well as of breaking con- 
nexion with the battery. In April 1837 I published, in Sturgeon’s 
‘ Annals of Electricity,’ a description of an instrument which I 
devised for producing a rapid succession of electrical currents in 
the coil by rapidly making and breaking communication with 
the battery. This, as Mr. Bachhoffner says in one of his papers 
published in Sturgeon’s ‘ Annals,’ was the first contact-breaker 
ever made. Thus, before April 1837 I had completed the coil 
as a machine for producing a regular supply of electricity. From 
1837 till the end of 1854 my attention was directed to other 
matters. Since the beginning of 1855, I made a long series of 
experiments on the various parts of the induction coil and appa- 
ratus. Although my experiments are not yet finished, I thought 
it better to lay the results already obtained before the British 
Association *. 
The following are the results of my experiments :—First, a 
method of getting a shock directly from the armature of a mag- 
net at the moment of its demagnetization ; secondly, the dis- 
covery of what I believe to be a new- fact or law connected with 
the action of iron on a battery by which it is magnetized, viz. 
that if iron be put into a coil of covered wire, the ends of which 
are connected with a battery, the quantity of electricity flowing 
from the same battery through another coil connected with it 
will be considerably greater when the first coil is nearly filled 
with iron than when there is little or no iron in it; thirdly, a 
* This paper was read in Section A. (on Mathematics and Physics) at the 
late meeting of the British Association in Dublin. The paper being hastily 
written, some things were omitted which are here supplied. 
