iment. The
developments were considered at the time of much importance in a
scientific point of view, and they subsequently furnished the means by
which magneto-electricity, the phenomena of dia-magnetism, and the
magnetic effects on polarized light were discovered. They gave rise to
the various forms of electro-magnetic machines which have since
exercised the ingenuity of inventors in every part of the world, and
were of immediate applicability in the introduction of the magnet to
telegraphic purposes. Neither the electro-magnet of Sturgeon nor any
electro-magnet ever made previous to my investigations was applicable to
transmitting power to a distance.

The principles I have developed were properly appreciated by the
scientific mind of Dr. Gale, and applied by him to operate Mr. Morse's
machine at a distance.

Previous to my investigations the means of developing magnetism in soft
iron were imperfectly understood. The electro-magnet made by Sturgeon,
and copied by Dana, of New York, was an imperfect quantity magnet, the
feeble power of which was developed by a single battery. It was entirely
inapplicable to a long circuit with an intensity battery, and no person
possessing the requisite scientific knowledge, would have attempted to
use it in that connection after reading my paper.

In sending a message to a distance, two circuits are employed, the
first a long circuit through which the electricity is sent to the
distant station to bring into action the second, a short one, in which
is the local battery and magnet for working the machine. In order to
give projectile force sufficient to send the power to a distance, it is
necessary to use an intensity battery in the long circuit, and in
connection with this, at the distant station, a magnet surrounded with
many turns of one long wire must be employed to receive and multiply the
effect of the current enfeebled by its transmission through the long
conductor. In the local or short circuit either an intensity or a
quantity magnet may be employed. If the first be used, then with it a
compound battery will be required; and, therefore on account of the
increased resistance due to the greater quantity of acid, a less amount
of work will be performed by a given amount of material; and,
consequently, though this arrangement is practicable it is by no means
economical. In my original paper I state that the advantages of a
greater conducting power, from using several wires in th