Year: 1878

II
. if a strip Of paper is moistened in a So
luton of say chloride of potassium, and
laid upon plate having connection with
one pole of a batteryand a flat platinum
strip having connection with the other
pole OF the battery is held by the hand
and drawn heavily over the surface OF
the moistened paper, there will be found
little or no friction between the platinum
strip and the paper, it gliding over the
surface like iron on ice. But, ifnow the
electric current is interrupted. the hand
will be involuntarily stopped, because
the current no longer passing through
the paper the normal friction of the
paper is instantly applied. Upon closing
the battery current while the hand is
slowly drawing the platinum strip over
the paper against the friction, the hand
will be instantly released, and involun-
tarily glide forward. With this differ
ence of friction obtainable BY the action
of electricity, Mr. Edison saw at once
that he could produce precisely the same
mechanical results as by the electro
magnet. The mechanism of this sub
stitute for magnetism may be varied in
a hundred ways; the simplest form,
however, may be thus briefly described:
A clock work is made to revolve flanged
metal drum. The drum carries over its
surface continuous strip of the chem
ically saturated paper, not too moist.
Piyoted at right angles with the drum is
a lever of brass with the free end pro-
Ijecting slightly beyond the center ofthe
drum; through this end an adjustable
screw with platinum or lead point is
made to rest upon the paper strip there
by supplying frictional surface. To
increase this friction to any desired ex-
tent consistent with the tenacity of the
paper an adjustable spiral spring is
placed under the lever to draw it down
ward upon the drum (the pivot of the
arm being double-acting, permits this
motion also). Two adjustable stops con-
fine the movement of the lever within
any desired limits. 1t will be seen that
the revolving of the drum will carry the
lever against the forward point by
means of the great friction imposed by
the pressure of the lever point upon the
paper. A second adjustable spring is
now made fast to the lever to pull it
backward against the friction, but being
adjusted so as not quite to overcome it.
the lever remains against the forward
point. The circuit is now made through
the paper from the lever to the drum,
and instantly the friction is destroyed
and the lever drawn back by the spring
against the back stop, remaining there
until the current is Withdrawn, when
the constant forward motion ofthe drum
as instantaneously grapples the point and
carries it forward. Here, then, we have
al, the functions of an electro-magnet for
telegraphic purposes.


This is regarded as Mr.. Edison's great
est achievement, and one destined. some
day, to prove of immense value. Its ex
traordinary delicacy may be appreciated
when it is stated that in the course of one
experimentitw it was made to give telegraph
ic signals through 10000 ohnas resistance
tby means OF q battery current that thro'
that resistance whuld not record trace
of itself upon paper stepped in saturated
solution of iodide of potassium.


The electro photograph telephone is an
invention based upon the above describ
ed principle of action, and is now demon
strating the marvellous range of action OF
this wonderful discovery by transmitting
the full compass of vocal and instrument
al vibrations over an ordinary telegraph
wire 200 miles sn length, reproducing
the tones with great accuracy. The vocal
vibrations are converted into electrical
impulses, thus:


A brass tube six inches long, two and
half inches in diameter, having mouth
piece at one end and thin metallic or
mica diaphragm stretched across the 9th
er end; in the center of this diaphragm
is fixed a delicate electric spring having
a platinum face. Through this spring is
passed cushion of felt, the object of the
hole being to prevent rebound. Imme-
diately in front of this is placed an ad-
Unstable screw with platinum contact
point. The diaphragm being connected
with the line and the adjustable point
with the battery. when the air waves are
thrown into the tube from the voice or a
wind instrument, the diaphragm re-
spends in unison, and at every outward
movement comes in contact with the bat
terry point, thus completing the circuit,
and of course, breaking it again upon its
receding from it. the whole constituting
key responsive to the vibrations of the
voice instead cf the touch. The electric
al impulses thus passed over the wire to
the distant end, comprising precisely the
same number per second as the air waves
which set them free, are made by means
of the electro photograph to vibrate a
sounding board like number of times,
and thus produce the original air waves
ofsound. The apparatus for effecting this
vibration is very simple.


A small hand crank with cog-wheel
attachments operates to give motion to
the metallic drum of the motograph a
strip of paper moistened in solution of
sulphate of sodium is carried over the
surface of the drum. A sounding board
ian old style dulcimer is used) is stood
upon edge, and brass arm fastened
rigidly to it projects outward to the cen
ter of the drum, lying PARALLEL with it.
A steel spring with platinum face is
fixed underneath this arm and made to
bear with considerable pressure upon
the paper Immediately over the center
of the drum. by means of an adjustable
screw which passes through the end of
the arm. Now when the drum is re
yolyed outward from the sounding board
the. paper is drawn under platin-
um faced spring attachment Of the arm,
and the sounding board is drawn out
ward by means of the friction imposed.
The current coming over the wire from
the distant station, passes through the
paper, destroying the friction, and thus
permitting the sounding board to drop
back to its normal position, and the
cessation of this current permits the
friction to be again imposed, and the
board again drawn out. This treble
electro chemical and mechanical action
is 30 instantaneous that the finest and
highest notes of the female voice are
perfectly and audibly reproduced 200