South Bend news-times. (South Bend, Ind.) 1913-1938, 1921-05-06
WAR DEPARTMENT
Is TESTING new
BLACK LIGHT
invisible Light Rays for Use in
Signal Corps Forms is
New Contribution.

WASHINGTON. May An i'm
portant contribution 70 the science
ot warfare IL expected 10 result from
experiments with black light" or
invisible light rays. now being con-
deducted by war department experts
Il was learned recently.
Major Gen. George .. Sauier. the
chief signal officer OF the army, and
radio expert Of international repute.
for months have been giving atten-
ton 10 the subject, and the expert
nents ne has conducted thus far
nave proved almost uniformly sue
cessful.
Black Light" the general ex-
planned, is the name that has been
given 20 light rays OF greater wave
<length than those at the red end
or the spectrum. or Of lesser length
than those at the violet end. The
construction Of the eye Is such that
these rays have no impression on
the optic nerve. and they are there
fore invisible under ordinary cir
cumstances. Nevertheless. they are
generated by every candle. lamp or
other source OF light. and scientists
have devised unquesuonable meth
DDS or determining their presence.
New Signalling Apparatus.
The experiments thus far conduct
ed with these rays by the army. Gen.
Squier stated. have dealt primarily
with the problem OF devising suit
able apparatus for utilizing them in
signalling. but their possibilities are
by no means limited 10 signalling
alone. While much or the detail
work remains 20 be done the
soundness OF t-e principle is be-
heved to have been demonstrated be
yond a doubt. and further practical
applications are merely a question
Of time.
The black light" signalling sys-
TEN as now conceived may be li1en-
ed to the ordinary heliograph used in
the army except that invisible light
rays are used instead OF the flash
of sunlight. as projected by mirrors.
The advantage in time Of war of the
invisible system practically incapa-
ole Of interception. over the hello
graph. is obvious. A further advan-
tage lies in the fact that unlike the
heliograph the black light" rays
can be generated artificially and
therefore are not subject TO weather
conditions.
The idea that monochrOmatic light
consists OF a succession Of simple
harmonic vibrations IN the ether.
and that the sensation Of color de-
ponds on the frequency OF those Vi
brations is believed 10 have been
originated by Dr. Thomas Young
early in the nineteenth century.
Young and Fresnel were able to de-
terrsline wave lengths ranging from
.0O0076 en-. at the red ED of the
spectrum to .OOOO39 en-. at the ex-
treme violet end. and. by means OF
a formula. calculated the number Of
vibrations per second.
Violet Rays.
They were apparently convinced Of
the existence Of invisible rays not in
cluded IN the spectrum. but made
little progress in their studies of
those phenomena. Later investigat-
ors showed conclusively that the in
fra-red rays as ultraviolet rays are
OF the same physical nature as the
luminous rays. differing from them
only by the greater or smaller
length Of the wave.
The experiments conducted by the
war department scientists have had
to do chiefly with the development
\, OF the most efficient means OF gem
NratinC BLACK light" the perfection
OF a device for projecting or trans
hitting those rays 20 great distance,
and the construction of a suita BILE
receiving apparatus for registering
the signals.
Like the Roentgen, or X-rays. the
black light" rays have the property
OF penetrating substances impervious
To ordinary light rays. thus permit
ting their separation from the lumi-
nous rays.
Gen. Squier became interested i'm
BLACK light through his studies of
radio telegra ply, a branch OF science
in which he is an acknowledged au-
thority About a year ago ne
startled the scientific world by his
announcement OF the successful
completion OF his invention of the
so-called wired wireless" system.
which permits or the use OF uninsu-
lated ocean cables.