Year: 1877

nineteenth century, namely, the electro
photograph telephone. A brief description
of it will show how entirely different IN
principle it is from that of Mr.. Bell. just
described. The transmitting apparatus
consists simply ofa long tube about two
inches in diameter, having one en'l Gov
cred with "A thin sheet brass diaphragm,
which is kept tight by stretching ring


In the centre of the brass diaphragm
is rivcted thin disk of platina and i'm
mediatcly in front OF this disk is an adj
Unstable platina-pouted screw txa rigid
pillar


To transmit the music it is only neces.
sary to sing "r play into the open end of
this tube. This causes the diaphragm
to vibnte and, the .platina points meet
ing make tlie circuit and the electric
current transmits every vibration over
the wire to the rec living end.


The receiving apparatus employed hy
My. Edison tor reproducing the tones is
based upon an original discovery made
Ivy him some five years ago. This dis
covery was that when piece Of paper
moistened with certain chemical solutions
is laid upon metallic plate connected to
the positive pole oI n battery, and pla-
tina-faced wire connected to the mega
tive pole OF the battery is drawn over
the paper, the passage Of the current
through it causes all friction to disappear,
and the patlna faced wire slides over
the paper MS from upon ice; bur il the
current be interrupted this effect instant.
ly disappears, and the normal friction
Of the paper causes the wires
to be drawn over it, with difficulty.
This principle is applied to the receiver
il resonant box, drum or wheel, hav-
ing flanges ON both sides. This wheel is
secured to shaft rotated by the handle.
A continuous strip Of piper from the
reel passes over the drum, the surface Oi
which is roughened Resting upon the
drum is smooth platina point upon the
end of the spring, which is secured to
the centre of the resonant box, and
presses the platina point with consider
able force upon the chemically prepared
paper. The current from the battery
passes to the spring, to the platina point
thence through the moist paper-which
in this state is conductor-thence to
the drum, and back to the battery.


The operation is as follows: "When
the handle is turned the paper passes
forward, and the normal friction between
the point aud the paper serves to give
forward motion to the spring hence one
side of the resonant box is drawn out.
If now a wave OF current passes through
the paper all friction ceases, and the
spring not being pulled, the side Of the
resonator regains its normal position: |:
and this takes place at each vibration.
by means of this friction the most feeble
currents. which would not producs the
slightest effect upon an electric magnet,
thus exert extraordinary strength. This
apparatus will respond and reproduce
with great power the highest notes of
the human voice, which are nearly in.
audible when magnets are employed, the
slowness of their operation heing due to
the time required for the maRnetization
Ct the iron cores, and the production of
secondary currents which delay the ac-
tion and mutilata the signals.


This description refers more especi-
ally to he apparatus for the transmitting
of the human voice in tones or singing.
The only difference between this and the
speaking telegraph proper, however, is
in the substitution OF plumbago point
LOT the platina point III the adjustable
screw of the transmltter. This, again, is
another original discovery of Mr.. Edi-
sons, viz, that plrmbago changes its
electrical resistance with enormous IA
pidity under pressure, the effect in this
application being that when the dia-
phragm is vibrated weakly contact is
made with the plumhago point very
lightly, and the resistance of the plum.
bago being but slightly reduced, weak
current is sent out from the battery, and
a weak effect produced at the receiving
station. When, however, a strong pres
sure Of the diaphragm is effected, by