The Stourbridge Observer, Cradley Heath, Halesowen & District Chronicle.
Stourbridge, West Midlands, England, 1879-05-31 00:00:00

THE EDISON TELEPHONE.

A very interesting and instructive lecture on the Edison
telephone has been delivered in London before the Society
of Arts by Mr. Conrad W. Cooke, Professor Tyndall, 1.R.5.,
being in the chair.

In dealing with his subject, which he pursued at
considerable length, the author traced the rise and
progress of the telephone, noticing its development at
various stages of its existence by its different practical
exponents. The first successful transmission of articu-
late speech to distance by means of electricity was
effected by Professor Graham Bell in 1876, as an-
nounced by Sir William Thomson at the meeting
of the British Association in that year. Prior to
that, however, Reis, Varley, La Cour, and Elisha
Gray had succeeded in transmitting musical notes
electrically as a,practicable and useful mode of signal-
ling. The details of these developments were
described by Mr. Cooke, after which he referred to
the thread telephone, and then described the present
Bell telephone. Mr. Edison's carbon telephone was
next brought under not ice, and its principles explained.
A reference to the crown telephone of Mr. G. M,
Phelps led up to the latest development of Mr. Edison
—namely, his loud•speaking telephone, which consists,
first, of a small chalk cylinder, specially prepared and
mounted ona horizontal axis, and revolved beneath a
metallic strip which is pressed upon the chalk, the
. latter being kept damp. At the point where the
strip rests upon the cylinder is a small plate of
platinum, and the opposite end of the strip is attached
to the centre of a diaphragm of mica, fixed to the
framing of the instrument by its circumference. By
connecting the strip to the zinc element of a voltaic
• battery, and the chalk cylinder to the copper pole, and
rotating the cylinder at a uniform speed away from
the diaphragm when no current is passing, the friction
between the moistened surface of the chalk and the
platinum strip draws the centre of the diaphragm
inwards. The moment, however, an electric cur-
rent passes between the strip and the cylinder,
electro•chemical decomposition takes place, the
friction is reduced, and the diaphragm flies
back. If a variable or undulatory current of elec-
tricity be transmitted through the instrument, the
diaphragm will be kept in continual motion by the
constantly varying friction existing between the chalk
and the platinum. By this means all the complex
sonorous undulations propagated by human articUla-
tion instantly produce their corresponding variations
of frictional resistance, and the diaphragm rep.ro-
duces, in a loud voice, the words which are being
uttered into the telephone at the distant station.
The working of this telephone was admirably illus-
trated by means of the only instrument at present in
this country, which is Mr. Edison's rough experi-
mental apparatus. Songs sung through it from a
distant room in the same building, tunes played on the
cornet, and also whistled, were reproduced with force
and fidelity in the Lecture-hall, to the gratification of
a crowded audience. _ _ _

At the conclusion of the lecture, Professor Tyndall,
in a complimentary spech, proposed a vote of thanks
to Mr. Cooke for his interesting lecture, which was
heartily accorded by those present.