The sun., 1912-07-14
Wheeled Stretchere for
French Army


light. which has made i, possible to tele.
graph photographs. which will keep the
burglar away from the family safe and
automatically put out oitys street
lights when dayhreak comes this little
known metal has very recently been
used to enahle the blind to hear what
they cannot soc Late cable de-pa, ches
tom London have trld how Dr Fourner
d'Alhe has employed sclcnium to make
- light audible.
The basis of ihi, latest wonder as of
all previous feat, achieved with sele-
mum. Is the metal, peculiar property
OF changing Its resistance to electricity
when light strikes il, In tho dark scle-
mum won't lot electricity 10y. Its re-
siSance To current is enormous. But
let a perceptihl" quantity of light i0to
the room and instantly your sClonium
becomes conductor Of ~" electric cur
rent. and rh" brighter the llEh, that strikes
il the better conductor il becomes.
So pr. d'Alhc. who is lecturer on
physics at Birmingham University, Eng
land. Went before the ois ical convention
at South krn-ington with little con-
trivance which he called the optophone.
bear light hut may locate it and estimate
its intensity. The instrument on,ains
selepium cell The light striking tie
metal makes il a conductor of electricity
and current flows through circuit.
This current is interrupted by a special
arrangement Of Pr. d'Albe's and is trans
mitted through telephone receivers fitted
TO the head of the blind man. He hears
sound varying in louchness with the
intensity Of the light If il is "a street
lamp he can 10y walking about it tell
almost exactly where IT stands. Moon
light is said To- be dist lnctly audible and
bright sunshine makes IA roaring noise.
The possibilities of such an instrument
DIR. d'Albc does not name. but they are
very great.
The invention depends upon the unique
property of the non metallic element.
seleniuin, of changing its electrical re-
sistance under the influence of light
This property was discovered accidental lily
in 1874 at the Atlantic cable station at
Valentia. County Kerry. Ireland. Sc
leniun was used there for insulating pur-
poses, and in the course of their work
the operators discovered that the pres
encc or absence of light caused annoying
irterferences with the proper working (
Of the apparatus. 1t was only three years
ago that Mr.. D'Albe thought of nir ming
this quality to practical use. and after
long experimenting he invented the opto-
pnone.
II consists of two parts, tho one a pair oi
high resistance telephones and the other
box ls inches kby II. ~nich con
tains s"lcnium plate. an electric bat
terry, resistance coils and q clockworl
interrupter. 4 tablet Of Staffordshre
porcelain il covered with deposit OF
graphite, and To and fro upon it lines ar,
ruled with diamond. Avapor deposit OF
seleni'im is imposed and fixed by an an,
healing process. The user fastens III,
telephQne to his ears. and as light OF
darkness falls upon the sensi'zed plate
he hears sounds of various degrees Of i'll
ten,ity.
4 newspaper man who tried tho OPTIC
phone with thick handage over his eyes
heard the shadow cast hy "A thick she"
of blotting paper as a ticking or raspinl
sound
Moonlight il appears. Causos n con
siderable ratt ling III III" ears, and sunligh
may bc recognized by "thc tremendous
noise il makes The mechanism may b,
adjusted 10 silence for light or "silenc,
for darknc~, a. may be most convenient
and the change from one condition to tn,
other Will produC" the sounds IN the tele
phones. In tn" course Of tho experiment.
at South kcnsngton a young man from
Leeds who was stone blind through diseas
of the optic nerves, was placed on on,
side Of the table with a telephone receive
fixed to his ears, and the optophone ad
iustrd Ia siLFnr" for light. On the op
poaite sid" of the room was n large higl
window, and betwccn il and the blin,
youth a number of men passed at inter
walls
"1hats "A man." exclaimed tho youth
sand that s "A man, he went on, kcopin
tally correctly as one after another passe
between the optophone and the Quite
daylight. lie recognized each obstruct io
without fail, ALTHOUGH a regiment Nigh
have paridod by without his noticin
It if lef' 10 his own unaiccd senses.
Another test applied was in equippin
blind man with the instrument "slcnce
for daPkn.ss He was then instrIcte
to walk around IA room and locate tn
Window This he did without any dtf1
culty, explaining that upon approachin
the light IN each case a ticking or raspin
sound became audible to him.
Ono o9 those who witnessed the espc.!
mcnts and who was gifted with sigh
commented on the cumbrousness Of th