To connect the two
instruments together upon a line, it is only necessary to connect the
two keys with one wire and the terminals of the two coils with another
wire, cutting one of these wires and inserting the battery.
[Illustration: FIG. 15.--MAGNETIC FIGURES.]
As soon as the operator ceases to work his instrument he should place
the key in contact with the contact point, and cause it to remain
there by slipping the end of the key under the head of the screw
provided for that purpose. The other operator can then proceed to send
his message.
Those who desire to practice telegraphy should learn the Morse
telegraphic code.
MAGNETIC FIGURES.
By arranging the coil so as to form an electro-magnet, as before
described, and holding the magnet under a plate of glass sprinkled
with fine iron filings, as shown in Fig. 15, and then sending a
current through the magnet, at the same time jarring the glass by
striking it with a lead pencil, a magnetic figure will be formed which
is sometimes called the magnetic spectrum. By connecting the terminals
of the coils diagonally with each other, and connecting the remaining
terminals with the battery, two like poles will be formed, and the
magnetic figures will have an entirely different appearance, owing to
the repulsion between the two like polarities.
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