The Redwood gazette. [volume] (Redwood Falls, Minn.) 1873-1940, 1879-05-08
EdisOn's ElectrO.MOtOgrsph.

THE following description of Edi-
sons latest invention is taken from a
paper on the subject in "The Worlds
Work. department of Scyibner for May:
In the electro-motograph q cylinder
made of prepared chalk and saturated
with strong solution of caustic alkali
is set upon supports SO that it can be
turned upon its axis. A strip of metal
fastened to the mica diaphragm rests
on the cylinder and is pressed SO firmly
by its spring upon the cylinder that
when it is turned by means of the
handle the friction of the strip on the
cylinder tends to pull the diaphragm
out of shape, causing it to bulge in
ward as long as the cylinder is in mo-
ton. If now, while tLis motion of the
cylinder is maintained, an electric cur
rent passes through the strip of metal
and then through the chalk cylinder to
earth, the amount Of this friction is
varied or it is destroyed altogether,
and the strip slides freely on the cylin-
der. This was the basis of the former
invention. The release from friction
by change in electric condition in the
first instrument failed simply from
ignorance of some slight matters of de-
tail, that in the electro-motograph are
corrected and made practical. In the
musical telephone the releasing of the
FRACTIONAL resistance by electric action
caused the sounding-board of guitar
to vibrate, and thus set up sonorous
vibrations. In the Acknowledgment
the mica disk takes the place Of the
guitar, and, by the improved construc-
ton of the apparatus, intricate and
complex vibrations such as are pro-
duced in speaking are reproduced in
their original or even in greater vol
ume. When the apparatus is at
rest the diaphragm is motionless,
and electric currents shot through
the apparatus produce no effect.
In the same manner the mere
turning of the cylinder without electric
action produces no effect, except to
pull the diaphragm slightly out of
shape. II while the cylinder is being
turned an electric impulse arrives, the
pull on the diaphragm caused by the
friction of the strip on the cylinder is
more or less released, and the dia-
phragm is free to vibrate or spring back
into its original condition. II, now, the
electric impulses follow one another in
regular order in correspondence with
the sonorous vibrations impaired to the
transmitting telephone, the alternate
slipping and catching of the metal
strip on the cylinder will follow in the
same order, and thus the diaphragm
will be made to vibrate in unison with
the original vibrations, and thus re-
produce the original words. As the
mica disk is much larger than the disk
of the transmitting instrument, the
amplitude of its swing may be much
greater, and consequently, it will re-
peat the words with greater power.
The electro photograph is practically
an apparatus for transforming electric
action received from q distance into
mechanical work. The amount of
electric action has nothing to do with
the amount Of the mechanical work
performed, because the movement Of
the cylinder is controlled by power in
dependently Of the electric action, the
electricity merely releasing this power
by destroying the friction In greater or