was still early in the nineteenth century that a model telegraph was
exhibited in London.

About this time two professors at the University of Göttingen were
experimenting with telegraphy. They established an experimental line
between their laboratories, using at first a battery. Then Faraday
discovered 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
Göttingen, 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.