12 REPORT—1857. 
but a coil of very fine insulated iron for the armature of an electro-magnet, between 
the poles of which the coil would fit. When the helix of the magnet is connected 
with a battery, the armature is magnetized on account of its proximity to the mag- 
netized iron; and when the battery connexion is broken, if the ends of the insulated 
iron wire be held in the hands, a shock will be felt. The second result is the dis- 
covery of the fact, that if iron wires be put into a coil of covered copper wire, the 
ends of which are connected with a battery, and if another coil be connected with 
the same battery, the quantity of electricity which will flow through the latter will 
be greater when the first coil is filled with iron wires than when they are removed. 
The third result is, a core for the primary coil, which consists of a coil of insulated 
iron wire, and which has five advantages over all the cores in common use. First, 
there is no complete circuit for any electrical current excited in any section of the 
core, because all the spirals of the coil are insulated from each other, and no spiral 
returns to itself. In the common cores, even when the wires are covered with 
thread, there is a complete circuit for every current induced in each section of every 
wire. Secondly, the currents in the various sections of the iron coil do not oppose each 
other ; but the currents in each section of every wire of the common cores are opposed 
by the currents flowing in the surrounding wires. Thirdly, in the iron coil all the cur- 
rents in the various spirals flow in the same direction, and form one strong current, 
which may be used by connecting the ends of the coil with any body to which we wish 
to apply its force. But in the common cores all the currents in the sections of each 
wire remain within the wires, and cannot be used. Fourthly, the effect of the condenser 
on the currents produced in the iron core can be ascertained when an iron coil is 
used, but not with the common cores. By using an iron coil as a core, it is found 
that the condenser increases the intensity of the currents induced in the core. 
Fifthly, the ends of the iron coil, used as a core, may be connected with the coatings 
of a Leyden jar, and then the sparks from the coil are diminished in length, but in- 
creased in brightness. By the use of cores cousisting of coi!s of insulated iron 
wires, electrical currents of considerable quantity and intensity may be obtained. 
These currents of quantity and intensity may answer for working the Atlantic tele- 
graph, and for producing the electric light. Besides the cores just described, and 
the common core, Prof. Callan used three other kinds of cores; viz. a flat or ellip- 
tical bundle of wires ; a core made by coiling uninsulated iron wire on an iron bar, 
and a core consisting partly of a bundle of iron wire, and partly of a coil of insulated 
iron wire. The fourth result of his experiments is a new mode of insulation, in 
which imperfect insulation is used when imperfect insulation is sufficient, and per- 
fect insulation is employed where such insulation is required. The advantage of 
this mode of insulation is, that each spiral in the secondary coil is brought nearer 
to the other spirals, as well as to the primary coil and core, than it can be in the 
common method of insulation, without at all diminishing the efficiency of the insu- 
lation. A coil in which the secondary wire was iron, and insulated in the manner 
described, was shown to the meeting, which, with a single cell, 6 inches by 4, gave 
sparks half an inch long without a condenser. The insulation of the large conden- 
sers made by Prof. Callan, in which the acting metallic surface of each plate exceeded 
600 square feet, gave way before the coil which he exhibited was made; and there- 
fore he could not say what the length of the sparks would be with the aid of a con- 
denser. But were a condenser of the proper size to have the effect of increasing the 
sparks in a thirtyfold ratio, as in Mr. Gassiot’s great coil, the length of the sparks 
produced by Prof. Callan’s coil with a single cell should be 15 inches. The outer 
diameter of the coil was about 4 inches, its length 20 inches, and the length of the 
secondary coil about 21,000 feet. The fifth result is, a contact-breaker in which the 
striking parts are copper, and which acts as well as if they were platina. The sixth 
result is a more satisfactory explanation of the condenser, which is confirmed by the 
effect of the condenser on the electrical currents produced in thecore. The last result 
consists in the discovery of some new facts relating to the condenser, from some of 
which it follows, that the ordinary mode of making the condenser is defective ; for con- 
densers are generally made so that the entire surface of each of the metallic plates 
must act. But the condenser for every coil should be constructed in such a way, that 
a small, or a considerable part, or the whole of the surface of each plate may be 
applied to the coil. Fora large condenser which would make the effect of a coil ex- 
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