The record-union. [volume] (Sacramento, Calif.) 1891-1903, 1897-06-06
REMARKABLE INVENTION.
Professor Bell TelephOning Along an In
tangible Wire.
A Delicate Instrument mat has
Actually Transmitted Speech
Through Sunbeam.

of empty spacei There IS nolhIhs'
probablv. which 10 the ordinary man
would seem more hopelessly Impossible
than this. To those who have some
knowledge of science the dlfhcully
would seem even more insuperaple.
Sound is the vibration Of air; in vac
uun silence reigns forever. II hfted
above the atmosphere, the widest
clangor of bells would be stified; the
heaviest cannon would hurl its bolt
without a whisper
How. then. is it conceivable that any
sound should ever be carried through
the interstellar void?
How signals might be transmitted to
the eye-from Mars, for example II
creatures of sufficient intelligence dwell
there's easily understood. But sound
that is quite another matter.
Yet science has solved the problem.
This does not mean that apparatus OF
sufficient power and sensitiveness have
actually been constructed: the difficult
ties in the way of an experiment on a
scale of such magnitude are too for
mfdable, and the cost would be ruinous.
But the means have been found; the
impossibiity has vanished, the remain
der of the problem is mere mechanical
detail Just as the telescope may con-
ceivably be perfected until we can see
the minutest objects and look the Mar
tan. if he is there, in the face, so, by
the perfecting of this new sort of tel
ephone, we may hear his words if he
has the gift of speech.
ON A SHAFT OF LIGHT.
For the instrument by which all this
&c l,a,a mil cd
~ be called a telephone-but with diff
ference. Of course, no wires can ever
be stretched from the earth to a flying
planet. There is but one possible me-
dunn.
1t is proposed to telephone along the
rays Of a shaft of light.
1t has not only been proposed; it has
alreay been done, though not yet
through interplanetary distances. But
if light can carry sound for a single
mile it can carry it to the ends of the
universe, and this perhaps is really no
more wonderful than the fact that
through light, by means of the spectre
scope, we can analyze the remotest star
and say with certainty that it contains
iron and sodium and other wellknown
metals.
Let us not be hasty in setting limits
to what science may do by unexpected
methods.
Photophone is a more exact name for
an instrument which carries words on
the wings of light, and so it has been
christened by it's inventor, Professor
Alexander Graham Bell who. ii is re-
ported, is now busily engaged in per-
fecting it.
His success in this bold attempt to
substitute a bundle of light rays for
the electric current and the telephone
wire depended upon a peculiar proper
ty possessed in any appreciate degree
only by the metal selenium. upon the
electrical properties of which light has
a marked influence. 1t was found that
when this metal, which in many Of its
chemical and physical properties re-
sembes sulphur and tellurium, is sub
jected for some time to a heat of 100
degrees and then slowly cooled it as
sumes a crystalline structure the cleo
trical properties of which vary remark
ably with the intensity of the light to
which it is exposed.
THE THEORY.
Thus a given specimen, the resist
ance of which in the dark was l 200
ohms, when exposed to diffuesd day
light showed a resistance of only 600
ohms.
Now when one talks through an or
binary telephone transmitter his voice
causes a thin sheet of iron diaphragm
TO vibrate back and forth, and this vi
bration causes a corresponding varia
ton in pressure upon piece of carbon
which forms part of an electric circuit
Thus the conductivity of the current is
varied, and what is called an undula
ting current results, the variations in
strength corresponding exactly TO the
compressions and rarefactions of the
air produced by the sound waves.
AT the other end of the line this
varying current of electricity is made
to pass through the coil of an electro
magnet, causing its magnetism to vary
in like manner and this, setting in vi
bration a second diaphragm in exact
synchronism with that in the trans
mitter, gives rise to air waves pre-
cisely like those produced by the
speaker.
Thus, although the sound itself is not
transmitted over the line as it is
through a tube, we have at the further
end an exact reproduction of the orig
NAL sound waves.
1t is clear that any other method of
varying an electrical current in CORE
spondence with sound waves would an
swer the same purpose. 1t was only
necessary to find a proper medium; and
in view of the peculiar property of
selenium already explained, it occurred
to Professor Bell that if he included
piece of this metal in an electric circuit
and could discover a way of varying
the intensity of the light that fell upon
ii, he could reproduce a series of sound
waves which in every particular would
echo those at the other end of the line
which gave rise to the variation. Ex-
pertinent proved his theory correct; he
succeeded, literally, in talking along a
ray of light.
SUCCESSFULLY DONE.
His mode of procedure is as follows:
Taking as his source Of light pencil
of sunlight admitted through small
aperture, or an arc lamp, the rays of
which We're rendered parallel by being
passed through a suitable lens, he re-
hected these rays TO the point where
the message was to be received by
means of a thin diaphragm Of mica,
which, being silvered, served as mir
ror
In order to intensity the effect par
abolic mirror was set up at the receive
ing station into which the rays were di-
rected, and by which they We're focused
at single point At this point was
placed a bit of selenium included in a
local telephone circuit, and the appara-
tus was completed.