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At this period he devised his electric pen, an ingenious device for making copies of a document. It consists essentially of a needle, rapidly jogged up and down by means of an electro-magnet actuated by an intermittent current of electricity.
Although to Morse belongs all the credit for the invention of the telegraph, it should, in justice to one man, be pointed out that it would have been impossible but for a discovery which preceded it that of the electro-magnet. To Joseph Henry, the great physicist, first of Princeton, then of the Smithsonian Institution, this invention is chiefly due.
A finished instrument was then made, having a transmitter formed of a double electro-magnet, in front of which a membrane, stretched on a ring, carried an oblong piece of soft iron cemented to its middle. A mouthpiece before the diaphragm directed the sounds upon it, and as it vibrated with them, the soft iron 'armature' induced corresponding currents in the cells of the electro-magnet.
He applied the property to the recording of telegraph signals without the help of an electro-magnet, by causing the currents to alter the friction between the two rubbing surfaces, and so actuate a marker, which registered the message as in the Morse system.
"There's a magnet in the casing which is powerful enough to swing the door to, after which the same magnet pushes this little bolt which looks like an ordinary screw into position, and that holds the door, but not very steadily. "You may say that this should have given me the criminal at once, but it didn't. "You see, this electro-magnet works whenever a current is turned into the wires.
These wires and magnets can be made to attract the little ball into any pocket the operator desires. Each one of those pockets contains a little electro-magnet. One set of magnets in the red pockets is connected with one button under the carpet and a battery. The other set in the black pockets is connected with another button and the battery. This ball is not really of platinum.
To get it out would apparently have demanded a painful and difficult surgical operation, as the piece of steel had entered the bone. But the head electrician, Petrio, simply placed near the wounded boy's face an electro-magnet capable of lifting five hundred pounds, and the sharp piece of steel instantly flew out of the cheek and attached itself to the magnet.
In this apparatus an electric current actuated an electro-magnet, which noted the instant of an occurrence by means of a pencil on a moving paper. It is said to have been capable of distinguishing 1/7300 part of a second, and the time a body took to fall from a height of one inch.
Hearing a submarine approaching beneath the surface, the merchantman may avoid her and the destroyers and patrol-boats may take means to effect her capture. From Lodestone to Leyden Jar The Mysterious "C.M." Spark and Frictional Telegraphs The Electro-magnet Davy and the Relay System.
When a current is sent into the electro-magnet, E, the brake shoe, F, is attracted, leaves the fly wheel, and sets free the jack, which continues to revolve until the current ceases to pass into the electro. The problem, then, is reduced to sending a current into the electro and in shutting it off at the proper moment. This result is obtained very simply by means of an auxiliary Leclauche pile.
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