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THE SPEAKING TELEGRAPH.

We have heretofore given accounts of the wonderful success of
Professor Bell in transmitting the vibrations of the human voice by
electrical means over a telegraph wire. He has lately made
improvements in his method of transmission, by which he dispenses with
the use of the battery, and substitutes the magneto-electric plan of
producing the current. The Boston _Transcript_ describes a recent
experiment with the new apparatus, by which conversation and singing
was successfully carried on between Boston and Malden, a distance of
six miles. The telephone, in its present form, consists of a powerful
compound permanent magnet, to the poles of which are attached ordinary
telegraph coils of insulated wire. In front of the poles, surrounded
by these coils of wire, is placed a diaphragm of iron. A mouthpiece to
converge the sound upon this diaphragm substantially completes the
arrangement. As is well known, the motion of steel or iron in front of
the poles of a magnet creates a current of electricity in coils
surrounding the poles of the magnet, and the duration of this current
of electricity coincides with the duration of the motion of the steel
or iron moved or vibrated in the proximity of the magnet. When the
human voice causes the diaphragm to vibrate, electrical undulations
are induced in the coils environing the magnets, precisely analogous
to the undulations of the air produced by that voice. These coils are
connected with the line wire, which may be of any length, provided the
insulation be good. The undulations which are induced in these coils
travel through the line wire, and, passing through the coils of an
instrument of precisely similar construction at the distant station,
are again resolved into air undulations by the diaphragm of this
instrument.

The experiments were as follows: Telephones having been connected with
the private telegraphic line of the Boston Rubber Shoe Company,
conversation was at once commenced. Stationed at the Boston end of the
wire, Professor Bell requested Mr. Watson, who was at the Malden end,
to speak in loud tones, with a view of enabling the entire company at
once to distinguish the sounds.

This was so successful that a smile of mingled pleasure and surprise
played on the features of those present. That it, however, might not
be supposed that loud speaking was essential to intelligibility, Mr.
Bell explained that soft tones co