The Wichita daily eagle. [volume] (Wichita, Kan.) 1890-1906, 1893-09-20
THE RADIOPHONE.
Talking Through Space by Means
Of Heat Rays
A Wonderful Invention of Pref. Bells on
Exhibition at the Worlds Fair
How the Instrument Il
Worked.

Exhibition at the Worlds Fair
How the Instrument Il
Worked.
Bells radiophone. by which CONVEX
sation is transmitted through space on
ray of light. no wires or electricity
being used in any portion of the appar-
atus, is one of the scientific wonders at
the world S fair. The photophone, 10y
which telephone is caused 10 re-
spond to the variations IN intensity of
a light ray falling upon a selenium
cell placed in local electric circuit is
familiar. Prof. Alexander Graham
Bell succeeded in transmitting articu
late speech in this way by making a
beam of light, which mirror reflects,
vibrate. the vibrations being of tho
same kind as those produced by speak
ing through membrane. He used a
thin mica or glass plate as diaphragm,
which by being silvered served at the
same time as a mirror. The reflected
ray of light rs it fell upon the selenium
cell at the distant point varied in in
tensity in unison with the sound waves
:" AAS1 SduoCt ShC WIZ WIN VI A-AC MIA
phragm mirror. The varying intensity
Of the light produces in the seleuiun
cell corresponding variation in the
resistance of the local circuit, and the
varying current which results there
from is translated into sound waves by
the telephone, which correspond exact
" with the sound waves which vibrated
The diaphragm. -
Prof. Bell pursued his Investigations
looking to obtaining sounds without
the addition of local circuit, and his
latest production, that which is now
about ready for exhibition in the Bell
telephone pavilion in Electricity build
ing, may be briefly described as fol-
lows: In the northwest gallery, over
hanging the main floor few feet,
there has been erected small plat
form, upon which the sending appa-
ratus is placed. This consists of q
focusing arc lamp of ordinary pattern,
whose rays, rendered parallel by lens,
are reflected from thin diaphragm
mirror to the receiving instrument
about eighty or ninety feet away, at
the north front of the Bell telephone
pavilion. The rejecting mirror is .
disk Of very thin glass, silvered on its
reverse side and held in heavy brass
frame by means Of washers of ordinary
plotting paper. Opening into the
chamber in the rear of this mirror Is
an ordinary speaking. tube, into which
the sounds are. uttereds causing the
mirror to vibrate as would the dia-
khragm Of telephone transmitter.
These rays, reflected in parallel
lines, are received at the farther end
by a parabolic reflector, in the focus OF
which is placed glass bulb, contain
ing small portion Of ordinary burnt
cork. The bulb is blown into the end
of glass tube about a quarter of an
inch in diameter and four inches long,
the other end of which is open, and to
which is attached an ordinary phono-
graph hearing tube, which extends
into small cabinet, where the liste-
ner, removed from external noises, re-
ceives the message. The only adjust
ments required are that the rays be
directed from the mirror in the gallery
in an axial direction into the parabolic
and that the bulb containing
the burnt cork be brought to the focus
of the parabolic mirror. This latter is
accomplished by pushing the glass
tube in or out until satisfactory re-
suits are obtained. Certainly nothing
could be simpler than this; but, al
though the instrument is of great sci
entifc interest. it has no apparent
practical value. The transmitted
as heard through the hearing
tubes, lack sharpness Of definition and
have somewhat mufled sound, which
is probably due to the tube effects.
The conversation can, however, be
fairly understood if one knows before
hand what is to be expected, but 1t
would be difficult to follow an ex-
preston for which one was not pre-
pared. Prof. Bell has given the fol-
lowing explanation of the philosophy
of the phenomenon: When the inter-
Inittent beam strikes upon the re-
ceiver, the particles are alternately
heated and cooled; when they are
heated they expand, and consequently
the intervals which are filed with air
are diminished; when the light is inter
cepted the particles are, cooled and the
spaces between them enlarged. Air is
out from the interstices be-
tween the particles in the first case
and drawn in in the latter; the enlarg-
ing of the intervals causes refraction
Of the air in the cork PARTICLES, and
the outer air rushes in; the contraction
Of the interstitial spaces causes con-
densation and escape of the air they
contain. These two effects are still
further increased by the heating and
cooling OF the air in the intervals al
ternately increased and diminished
By these means alternate waves CT
and rarefaction are pro-
duced in the surrounding air, and 1t Is
to this that the sound which is
emitted owes its existence.
Interested in Pomeiogy.