The Portland daily press., 1896-10-31

A"SAoS AoAo0 ono pEopofty VI tneSo
prisms to stop the light is destroyed or
counteraoted, and If the magnetism Ia
strong enough the light will pass
through as well as If there were no OBJ
struction.
LIGHT VARIES WITH CURRENT.
The power of the Nicol prisms varies
with the strength Of the magnet which
inoloses them; the strength of the mag
net varies with the strength of the cleo
tire current which passes around it; SO
the light passing through the prisms
varies with the electric current The
light falling on tho plate of the receiver
is thus made dependent upon that falling
on the plate of the transmttter. For the
variations in the ourrent are effected by
the action Of the light passing through
the picture impressed upon the plate Of
the transmitter. This light acts on
piece Of selenium in suoh way as to
change Its resistance to the passage of
the electric current and regulate its flow.
It's strength in accordance with the
strength of the current passing around
it, and the amount of light that can
pass through the prisms and fall upon
the plate Is regulated by the force of the
magnet
If the two disks in the transmitter and
the receiver were kept stationary all
that one would see at the receiving end
would be spot Of light, increasing and
decreasing in brightness. But II the
disks are made to revolve, both at the
same velocity, and at the same time the
sliding plate 10 given side wise motion,
one would see spiral line Of light. If
the plate is fed out very slowly SO that
the hole will move outward its own
width while the disk is making one
turn the spiral lines will be 50 close
together that all the surface of the disk
will be passed over after a sufficient
mum Der of revolutions have been made
to feed the hole all the way out to the
circumfsren ce.
To produce photograph at the rsceiv-
ing end is would be sufficient for the
two disks 10 Yevolvs at the same velocity,
because the spot Of light, even il it
moved slowly. would act upon photo
graphic plate. In order, however, that
a picture may be produced that can be
seen by the eye the velocity with which
the eye could see instantly this apparatus
would be Of no value for the purpose of
reproducing visible pictures. but the eye
does not see instantly.
PICTURE IN THE RECEIvEK.ss
If the disks are revolved with sufficient
rapidity to enable the spot Of light to
ira vel from the center to the outside be-
fore the image impressed upon the eye
has faded away the entire picture will
be seen.
1t may appear to be a difficult matter
to make two machines hundreds Of miles
away rotate In unison with each other,
but there are several ways in which this
may be done. The attainment Of the
very high velocity needed is far more
difficult matter, but some of the diff
Guilty in this direction can be removed by
reducing the size of the pictures, and
therefore Of the disks. If these are made
smaller fewer turns will be required for
the spot Of light to travel from the center
to the circumference.
Thers could be no objection to making
the pictures small, because they can be
enlarged before reaching the eye. There
fore the disks can be made as small as
one inch, or even smaller, and on ao-
count of this diminutive size can be TO-
tatsd at d high velocity with far less
difficulty than would seem possible.
The greatest difficulty, perhaps, is the
proper adjusting of the variation of
the lighu In the transmirter to the vari-
alton of the strength of the electric cur
rent. 1t is simple enough to cause the
changes In the intensity Of the light fall
Ing upon the selenium strip to vary the
flow of the electric current, but to SO
adjust the two that the change in one
may be in exact proportion to the change
in the other is quite different matter
The same is true of the action of the
upon the magnet, and Of the
latter upon the amount Of light passing
through the Nicol prisms.
In theory. at least, the instrument fs
perfect. 1t is believed that it can be
made equally perfect in practice. The
difficulties yet to be overcome are slight
In comparison with those already sur.