The sun., 1912-07-14

which, in the form tho photographers
call "A negative" is wound on a glass
cylinder. 4 totally rejecting ,nism
placed inside the glas9 cylrj'cr Projects
the light which penetrate ;no ri'p urcn
a sclenium coll situated ~ tho ord of the
cylinder. The point of light travels rni,e
by mite over the surface Of tho film as
the cylinder slowly revolvcs and rene
trates n the prism, which shoots il out
to the cell
dark spot in the film let's little ligh,
through. tho bright portions admit the
light nearly unabated and the light and
shadow of the picture, the light and
shadow that make the picture. are trans
mitted inch by inch and minute ly min
utc To the solenum cell. The coll. being
intensely sensitive to light, sends vary
ing electric current according to the
quantity Of light that hits it,
Al the receiving station cylinder
which nvolves in unison with the trans
mitting one is covered with a photo
graphic film. a blank ono. Upon this
film pencil of light from Nernst lamp
s concentrated. This light is kept from
the film when the SO selcniim cell at the other
end of tho wire sends no current and n
shutter admits the light Ia the film when
current exists and admits il proper
tionally to the strength Of tho current
Thus the original photograph Is copied
faithfully detail by detail and miles
away.
Mr.. Hammer. who is perhaps a. special
student Of selcniim as any man in
in l.11. A.
Stevens Institute of Technology gave
other picturesque and practical uses
to which selenirm may be put II can
he used a. burglar alarm by placing
q cell OF it before the safe .t needs
to be guarded.
| The light from the yeggmans lantern,
It matters not how noisclcss or skilful
he may be- will instantly make tho sele-
mum conduct,va. an electric current
will be formed ani through a series Of
relays tremendous alarm will dis
, turb the whole house before the burglar
can put his fingers on the combination.
One day MIR. Hammer was grollinR
about the West Side, 1t was morning.
He saw man with heavy toll lftink
the iron shutters on factory. There
| N'lF u i't W IIl' tlkHltt'T WAS
| stirred to work out n method of having
the shutters opened automatically. The
suns rays striking tho trusty selenium
coll would do it. That starts the electric
current. which u relayed. ard the shut
ters go up by electricity. A side device
would shut them at night in tho same
fashion or the glare Of nearby fire might
be made to close them and protect the
building
The proximity of n hostile fleet may
be detected at night by the seleniln
cell The moment the scarchlght of a
battleship strikes the fort selenium will
respond with current which. properly
relayed. will lift all the guns. aim then,
along the line of the battlcship's ray
and fire them instanter. Unfortiiled
bits of shore can he protected in this
way, You need only set up your cannon
and your seenium cell. No soldiers
are needed TO aim or fire il. The enemy I
searchlght will do that
There ara countless WAYS ~ using
esleninm's sensitivcness t. light for
detecting gases and fires in mines and
turning on sprinklers that will put ont tbs
Arcs The ordinary aT,oma,ic IRE alarm
in factories and the coordinated auto
matte sprinklers for putting cut q bAzs