Indiana daily times. [volume] (Indianapolis [Ind.]) 1914-1922, 1921-06-03
BLACK LIGHT
is TESTED BY
SIGNALCORPS
Invisible Rays Form New Con-
tribution to Science of
Warfare.
RADIO MEN INVESTIGATE

WASHINGTON, June 3-An i'm
portant contribution to the science of
warfare is expected to result from expert
ments with "black light" or invisible
light rays. now being conducted by War
Department experts, it was learned re-
Gently.
Maj. Gen. George o. Squier. chief signal
officer of the Army, and radio expert of
International repute. for months has been
giving attention TO the subject, and the
experiments he has conducted thus far
have proved almost uniformly successful.
BLACK light" the general explained, in
the name that has been given to light
rays OF grester wave length than those at
the red end of the spectrum, or of lesser
length than those at the violet end. The
construction of the eye is such that these
rays make no impression on the optic
nerve, and they are therefore invisible
under ordinary conditions Nevertheless
they are generated by every candle. lamp,
or other source of light, and scientists
have devised unquestionable methods of
determining their presence.
SIGNALLING
APPARATUS.
The experiments thus far conducted
with these rays by the army, General
Squier stated, have dealt primarily with
the problem of devising suitable appar-
atus for utilizing them in signalling, but
their possibilities are by no means lin
tied to signalling alone. While much Of
the detail work remains to be done, the
soundness of the principle is believed to
have been demonstrated beyond a doubt
and further practical applications are
merely question of time.
The black light" signalling system as
now conceived may be likened to the
ordinary Photograph used In the army
except that invisible light rays are used
instead of the fash of sunlight, as pro-
jected by mirrors. The advantage in
time of war of the invisible system, prac-
tically incapable of interruption, over the
heliograph, is obvious. further advan-
tage lies in the fact that unlike the
Photograph the BLACK light rays can be
generated artifcially and therefore are
not subject to weather conditions.
The idea that monochromatic light con-
sists of a succession Of simple harmonic
vibrations in the ether, and that the sen,
sation of color depends on the frequency
of those vibrations is believed to have
been originated by DR.. Tohmas Young
early in the nineteenth century Young
and Fresnel were able to determine wave
lengths ranging from .000076 en-. at the
red end of the spectrum to .000039 en- at
the extreme violet end and, by means of
formula, calculated the number Of vi
brations per second.
INFRA-RED AND
ULTRAVIOLET RAGS.
They were apparently convinced of the
nxiStonrn 0f invisible In al, la
in the spectrum. but made little progress
in their studies of those phenomena.
Later investigators showed conclusive
ly that the infra-red rays as we'll as the
tra-violet 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 War
Department scientists have had to do
chiefly with the development of the most
efficient means of generating "black
light" the perfection of a device for
projecting or transmitting those rays to
great distance, and the construction of a
suitable receiving apparatus for regis
tering the signals.
Like the Roentgen, or X-rays. the
"black light" rays have the property of
penetrating substances impervious to or
binary light rays, thus permitting theh
separation from the luminous rays
General Squier became interested in
"black light" through his studies of
radio telegraphy. branch Of science in
which he i san acknowledged authority
About year ago he startled the scientific
world by his announcement of the sue.
cessfuI completion of his invention Of
the so-called wired wireless" system,
ocean cables.