The Saint Paul globe. (St. Paul, Minn.) 1896-1905, 1896-10-12
BELLS RADI0pH0NE
a TELEPHONE IN WHICH SUM-
BEAM REPLACES THE
WIRE.
X RAYS SOUND TRANSMITTERS
HOW THE FALL OF SHADOW
MAY BE DISTINCTLY
HEARD.
X RAYS SOUND TRANsMITTERS
hAD1oPHoNE IN ARMY WORK.
Prof. Bell VIII Try to Develop His
Invention for Commercial
Use.

Prof Graham Bell is devoting his
attention to the commercial develop
ment of an invention of his which in
wolves nothing less than telephoning
by a ray of light
Perhaps not a single reader of this
article is aware of the fact that near
ly twenty years ago Prof. Bell made
the discovery of a method by which
he could hear a shadow fall. He found
in following up the researches of DR..
Werner SiemenS that the rare metal
called selenium possesses the peculiar
quality of varying its electrical con-
ductivity under the action of light
That is to say, its resistance to the
passage of a current of electricity diff
fers widely when it is exposed to the
light or hid in the dark. 1t was from
this discovery that the inventor de-
Vised an instrument as simple as it's
powers were astonishing. He found
that by connecting a cell made of this
metal, selenium, with the ear, by
means OF an ordinary telephone, and
then directing upon this cell an inter
rupted beam of light, he could detect
sound. 1t was at first supposed
that this rare metal was the only
one which possessed this quality of
being sonorous-that is to say, of Civ
Ing out sounds-under the action of
light; but In a series of experiments
Prof. Bell found that all substances
possess It more or less in the same
way when made up in the form of
thin discs or diaphragms. In a word.
the great inventor laid bare for the
first time new principle of matter.
1t was out of these researches that
the wonderful instrument upon which
Prof. Bell is now again at work sprang
he gave 1t originally the name of the
photophone. 1t aimed TO substitute
Tor the ordinary telegraph or telephone
wire ray of light. Doubtless there
Is many man who would question
the sanity of any one who would con-
tend he was able to talk for long dis
lance over a sunbeam And vet this
is exactly what Prof. Bell has succeed
ed In doing. The mechanism which he
devised does not differ widely from
the telephone in its general principles
save in the fact indicated, that it sub.
stltutes ray of light for the usual
copper wire
There is, first of all, transmitter
winch Is made up of a thin diaphragm
OF mica or of some other substance
SllVered at its back so as to make Of
1t rejecting mirror. The diaphragm
Is connected with an ordinary speaking
tube, into which the operator talks iust
exactly as he would talk into the
transmitter of a telephone Against
this thin disk or diaphragm is pro
Iected ray of light, preferably sun
light. The light is caught by a mir
TOT, ana directed through a concentrat-
ing lens whose focus is the transmit
ting diaphragm. The latter in turn
reflects the ray through a second lens
AOAin ms la ln
the ray Of light parallel, so that it
may travel any distance without dis
perSion
AT the other station, where the re-
celVlng operator is, there is a parabolic
reflector, at the end of which is fixed
selenlum cell. The cell in turn is
connected, telephonically. with the ear
Now, when the ray of light is reflected
from the transmitting diaphragm and
the operator speaks into the tube
joined with the latter, what he saws
may be clearly and distinctly heard at
the other end of the line, that is. at the
other end of the travelling ray of light.
ana that, practically speaking, is all
there is to this wonderful affair."
Inc theory upon which this instr,1-
ment is built is that the ray of light
may be impressed with sound vibra-
tons In exactly the same way that an
electrically charged wire is IMPRESSED
With the sound vibra tons from the tel
ephone When you talk into the tele-
phone, what takes place is simply
TINS; The electrical current being
prought into connection with the car
bon diaphragm, against which vour
voice strikes. the wire or current is
set In vibration, or rather the sound
vibrations or waves are impressed upon
the electrical vibrations or waves inst
as II You were to start a series Of
rlpples in a pond and then add to these
second series Of a different character
which would follow in the same direc-
ton, but not the same line of vihra-
ton or wave motion
1t follows from the process hero doc
cr1Oed, that If speaking against the
carbon transmitter will set up such an
agitation in an electrically charged
wire, mechanism which shall lust re
verse the action of the transmitter will
reproduce similar set of vibrations
upon diaphragm at the other end OF
the me ana thus reproduce your
speech.
AS the reader is doubtless aware all
TIE trend of modern physical science
is toward establishing the close reIa-
tiCnShip Of the different forms of mole
cCIar motion, which for the purpose of
olstlnctlon, are variously called light.
electricity, and sound. SO close indeed
is this relationship that the late Prof
Tyndal1, the highest authority on the
subject. wished to abolish some ~
these phrases, notably that of light /"
as simply confusion. And the further
science has gone the more it has come
to see that the only difference between
these varying modes of motion. the only
dlHererce between light and heat and
eicculcltJ and sound is the difference
or form 2 I'D rapfdity 1t has found that
1t is not very difficult to convert the
one into the other. The conversion OF
neat or electricity into light is so famil-
lat and commonplace process that
persons 10 not wonder at 1t at all. Rut
wAen Prof Bell went a step further
ana demonstrated the possibility of
converting light into sound, or at least
OF causing wave of light to produce
wave of sound, he entered into a
new fad END welded new link in the
chain oe relationship and interdepend-
ence. You will see that it was hut a
step further than this to his telephon-
Ing by light.
But 20 say that this is ''telephonine
by means of a sunbeam" is really q
very crude and Inaccurate description
or what actually takes place. This was
what Prof. Bell discovered by accident
ore Gay in the course of his expert
ments. y CHANGED that he thrust in
the path Of the ray a disk of India rub
VEL di'd re Iound th2t communication
was not interrupted in the least. The
accident told Prof Bell that he had
made yet further step in his re-
searches: that he had opened a new
gate to further knowledge of the sub
Ject. He had discovered that the process
OF telephoEing was not conducted by
the visible rays Of The sunbeam at ali.
but by the invisible rays. of which
there is knowledge only by inference.
If YOU sDlit I'D sunbeam NY rnears
of + prism on each eide of the spectrum.