as interesting to follow an invention from the original model
through the faultier types to the finished apparatus.

In 1860 Philipp Reis, as we have seen, produced a telephone which could
transmit musical notes, and even a lisping word or two; and some ten
years later Mr. Cromwell Fleetwood Varley, F.R.S., a well-known English
electrician, patented a number of ingenious devices for applying the
musical telephone to transmit messages by dividing the notes into short
or long signals, after the Morse code, which could be interpreted by
the ear or by the eye in causing them to mark a moving paper. These
inventions were not put in practice; but four years afterwards Herr Paul
la Cour, a Danish inventor, experimented with a similar appliance on a
line of telegraph between Copenhagen and Fredericia in Jutland. In this
a vibrating tuning-fork interrupted the current, which, after traversing
the line, passed through an electro-magnet, and attracted the limbs of
another fork, making it strike a note like the transmitting fork. By
breaking up the note at the sending station with a signalling key, the
message was heard as a series of long and short hums. Moreover, the hums
were made to record themselves on paper by turning the electro-magnetic
receiver into a relay, which actuated a Morse printer by means of a
local battery.

Mr. Elisha Gray, of Chicago, also devised a tone telegraph of this kind
about the same time as Herr La Cour. In this apparatus a vibrating
steel tongue interrupted the current, which at the other end of the line
passed through the electro-magnet and vibrated a band or tongue of iron
near its poles. Gray's 'harmonic telegraph,' with the vibrating tongues
or reeds, was afterwards introduced on the lines of the Western Union
Telegraph Company in America. As more than one set of vibrations--that
is to say, more than one note--can be sent over the same wire
simultaneously, it is utilised as a 'multiplex' or many-ply telegraph,
conveying several messages through the same wire at once; and these can
either be interpreted by the sound, or the marks drawn on a ribbon of
travelling paper by a Morse recorder.

Gray also invented a 'physiological receiver,' which has a curious
history. Early in 1874 his nephew was playing with a small induction
coil, and, having connected one end of the secondary circuit to the zinc
lining of a bath, which was dry, he was holding the other end in his
left hand. While he rubbed the zin