The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

INDUCED IMAGNETISM. 109
tion is effected as perfectly, though more feebly, when the bodies
are separated by space. ig. 7
Figure 7 represents a bar, -
magnet MI, and an iron rod
B, near together. By the
influence of the magnet 1i upon the principles of induction, the
rod B partakes of the magnetism of iI, the end N becoming
boreal and the end s azustral. If the rod B be brought in contact with the bar ri, the induction will be much stronger.
If to the north pole (fig. i. 8
M Fig. S.
8) of an artificial steel mag- A B C I,
net A, is placed a soft iron bar, <:,
n, the end s of B will instantly acquire the properties of a south pole, and the opposite end N, those of the north pole. The opposite poles would
have been produced at N and s, if the south pole s of the magnet; A, had been placeec near the iron B. In like manner, the
piece of soft iron B, though only temporarily magnetic, will render another piece of iron, c, and this again another piece, D,
temporarily magnetic, north and south poles being produced
at the ends. This represents compound induction.
It is important for the reader to observe the pointed analogy
between the phenomena of magnetic attraction and repulsion,
and those of electricity. In both there exists the same character of double agencies of opposite kind, capable, when separate, of acting with great energy, and being, when combined
together, perfectly neutralized, and exhibiting no signs of activity. As there are two electrical, so there are also two magnetic powers; and both sets of phenomena are governed by the
same characteristic laws. So also in the last experiment, the
magnetism inherent in B, Cg D, is said to be ijndtced by the
presence of the real magnet; and the phenomena are exactly
analogo'us to the communication of electricity to unelectrified
bodies by induction, the positive state inducing the negative,
and the negative the positive, in the parts of a conductor placed
in a state of insulation, near an electrified body. Where two
or more wires are suspended on the same set of poles, the
voltaic current transmitted on one wire will escape to the other
wire by induction, though not to a very great extent. If the
wires are placed near together, more or less of the electric influence will pass from one to the other, Figure 9 is another
representation of the inductive principle. Plunge a U-magnet
into a cask of nails and on withdrawing it the nails will adhere to the magnet and to each other as represented in the
figure. If the magnet be placed in connection with iron filings,
they will collect on the poles as seen in figure 10.