The Portland daily press., 1896-10-31
SEEING AT A DISTANCE.
Invention by Which Images Of Oh
jects Are Transmitted.
DESCRIPTION OF THE INSTRUMENT
BY WHICH 1T Is DONE.

Pictures Are Carried by an Electric Cur
rent Passing Through q Piece of Selen-
ium. the Resistance of Which Varies
With the Light Falling on It.
For quarter of a century science
has been laboring with the problem of
seeing at a distances problem more
difficult than that solved by the inven-
tion OF the telephone, though in it's gen.
eral characteristics somewhat similar.
Recently 1t has become evident that the
solution of the problem is at hand; that
1t Is a matter Of but short time before
It Will be possible for man seated at a
desk in Chicago to keep an eye upon
happenings in New York ana in San
Francisco at the same time, with the
surety that what he sees comes to him
first hand and not through the interven
ton Of photograph or artists sketch.
Indeeed the solution of the problem
has already been found and the only
difficulties to be su.mounted before
sight at a distance becomes fact are
mechanical and far from inconquerable.
Control of the rays of light has been OBJ
tanned and the barrier between this and
the production of pictures before the
eye Is but a slight one.
The apparatus by which so much has
been accomplished has been described by
William Baxter, Jr., in the New York
World, and from what 1t has already
made possible one can draw conclusions
as to what it will yet bring about. By
the method of the machine the picture
of the object to tie ssen Is impressed upon
plate at the transmitting end of the
instrument, transmitted by an electric
current, and reprod ucsd upon another
plate ut the receiving end. The distance
to which it Is transmitted has no effect
upon the picture. By using an adapta-
rion Of she magic lanterns 1t is pos.
sible to throw the picture upon screen
greatly magnifed.
Both transmitter and receiver are pro-
vided with a. revolving disk. located be-
hind the plate upon which the image is
received and as close to it as can be
without touching it. Each plate is ID
arranged as to move from the center to
the outer edge of the disk and back.
When tie plate is in it's central position
small hole, not larger than pin point,
comes directly over the center of the
disk. In the transmitter back of this
hOle there is piece of selenium. The
selenium is the key to the solution of the
problem, for it possesses the property of
changing its resistance to the flow of an
electric current by the action of light
upon IL. In the dark the resistance Ia
great; in bright light the current pas
ses through it freely. When the light
passing through the plate is not strong
the resistance of the selenium Is high.
If the disk is moved so as to allow more
light to pass through, the resistance of
the selenium decreases.
HOW. A PICTURE Is TRANSMITTED.
The electric current winch passes
through the piece of selenium repro
duces the picture at the receiving end of
tho insfrr mont. The amount of light
which can pass through any part of thu
plato and fall upon the selenium ia de-
pendent upon the shading at that
point, and the resistance of the ssleni-
um varies with the light which falls on
it; SO the current of electricity Ia regu-
lated by the lights and shadows of the
picture on the plate of the transmitter.
Az the receiving end the electric cur
rent is passed around an electromagnetic
made in the shape Of tube. SO that
light may be passed through it, the force
of the magnet being used to regulate the
amount Of light that passes through the
tube. This magnet is fixed back of the
revolving disk of the receiver in such
d position that the center Of the tube is
In lins with the pin hole in the sliding
plate.
A lamp is placed SO that its light will
shine through the tube and the hole In
the sliding plate and fall upon the plate
on which the picture is to be reproduced.
The tube has two Niool prisms, ons be-
ing placed at eaUn end and at right
angles to each other. These prisms are
made of Iceland spar and possess ;. the
property of icing transparent when in
certain positions, but if arranged at
right anglss shut off the light as. effect |
ually as il they were made of an opao ne |
substance. Under the action of the