covered that an electric current could be generated in a wire by
the motion of a magnet, thus laying the basis for the modern dynamo.
Professors Gauss and Weber, who were operating the telegraph line at
Goettingen, adapted this new discovery to their needs. They sent the
message by moving a magnetic key. A current was thus generated in the
line, and, passing over the wire and through a coil at the farther
end, moved a magnet suspended there. The magnet moved to the right or
left, depending on the direction of the current sent through the
wire. A tiny mirror was mounted on the receiving magnet to magnify its
movement and so render it more readily visible.

One Steinheil, of Munich, simplified it and added a call-bell. He
also devised a recording telegraph in which the moving needle at the
receiving station marked down its message in dots and dashes on a
ribbon of paper. He was the first to utilize the earth for the return
circuit, using a single wire for despatching the electric current used
in signaling and allowing it to return through the ground.

In 1837, the same year in which Wheatstone and Morse were busy
perfecting their telegraphs, as we shall see, Edward Davy exhibited a
needle telegraph in London. Davy also realized that the discoveries
of Arago could be used in improving the telegraph and making it
practical. Arago discovered that the current passing through a coil of
wire served to magnetize temporarily a piece of soft iron within it.
It was this principle upon which Morse was working at this time. Davy
did not carry his suggestions into effect, however. He emigrated to
Australia, and the interruption in his experiments left the field open
for those who were finally to bring the telegraph into usable form.
Davy's greatest contribution to telegraphy was the relay system by
which very weak currents could call into play strong currents from
a local battery, and so make the signals apparent at the receiving
station.

IV

INVENTIONS OF SIR CHARLES WHEATSTONE

Wheatstone and His Enchanted Lyre--Wheatstone and Cooke--First
Electric Telegraph Line Installed--The Capture of the "Kwaker"--The
Automatic Transmitter.

Before we come to the story of Samuel F.B. Morse and the telegraph
which actually proved a commercial success as the first practical
carrier of intelligence which had been created for the service of man,
we should pause to consider the achievements of Charles Wheatstone.
Toget