El Paso herald. (El Paso, Tex.) 1901-1931, 1913-02-20
Light Invisible to the Eye
Rays that VIII Not Penetrate Glass
Have Been Found that Xii
Billions of Germs.
ErraHarf. L
-ASHINCTON u. q Feb

gress Of science brought home
more strikingly than IN the develop
ment Of our knowledge of invisible
light. Not only has the scientist dis
covered rays OF light which the human
eye has never seen and can never see
/ but he has found how to use that
knowledge for the benefit of our every
day life. He has. found rays of light
so weak that ordinary glass, however
transparent to the vision, shuts IT out
effectively; and yet they are so
strong that billions OF germs may be
killed by merely coming within the
scope Of their influence
brilliant Lights in Darkness.
From the dawn of creation to the
recent past they have shed their in
flUence upon men, yet men have been
wholly unconscious Of their existence.
In the few short years that have gone
by since their discovery we have dem
onstrated that even in the inkiest of
darkness there may be brilliant lights.
such paradox could not be believed
by the ordinary layman did not the
eye Of the camera reveal its truth
That instrument shows Us that the
eye is sensitive to only a very small
proportion OF the total radiation that
scientist to believe that If the eye
could recognize all the radiation it
would reveal a thousand wonders IN
dreamed Of Gradually the scientist is
are capable Of detecting what the hu-
man eye cannot perceive, and it is be-
neved that many new things viii IL
timately be learned through them.
Remarkable Demonstration
Dr. p ". Wood, professor OF exc
perimental physics at Johns Hopkins
university, is one OF the worlds author
tiles upon Invisible light, and he Illus
trates some Of the remarkable things
about invisible light. For instance, he
says that If the finger he dipped into
zinc oxide and rubbed over a white
sheet Of paper the eye viii be unable
to detect the presence Of the streaks
of the white powder, unless it has been
very thickly applied If, however. that
piece Of paper be photographed with
ultra violet light, 1t appears to be
marked with streaks Of charcoal This
experiment led to the deduction that
If the moon and the planets be photo
graphed with invisible light substances
which do not appear usually might be
brought out
DR.. Wood had constructed a 16 inch
mirror, of &c inch focus, coated with
nickel, which he used in combination
with a plate OF the new ultraviolet
glass, heavily silyered-
Crater OF Moon Photographed
The region around Aristarchus, one
Of the craters Of the moon, was photo
gFaphed with yellow and then with
ultraviolet light. Then two specimens
a similar way. It was found that the
one sample when photographed with
ultraviolet light, correspondent iden-
tically with the deposit surrounding
the crater Aristarchus. 1t was anal
wed and found to contain iron and
traces Of sulphur. Then several rocks
were coated with iron oxide, and they
were photographed with the ultra
violet rays, but the iron showed none
Of the peculiarities of Aristarchus when
so photographed. After this an in
visible coating Of sulphur was formed
on a piece Of light gray rock by the
application Of a fine Jet. When it was
photographed with the invisible rays
it was black, exactly like the crater
Aristarchus-. From this DR.. Wood was
able to infer that this spot on the moon
is an extensive deposit OF sulphur, re-
sulting from vapor elected from the
crater.
Mysteries OF Light
In explaining the mysteries OF in
visible light before the Royal Institu-
ton Of Great Britain, DR.. Wood took
two pieces Of scarlet silk. which could
not be distinguished under an mean
descent light and placed them under
a COOper-HeWett mercury arc lamp,
with the result that one continued to
appear scarlet, while the other ap-
peared almost black. The mercury
lamp gives off almost no red rays, con-
seQueutly red objects appear almost
black. But the other piece of silk
Wae IuAc4 Gu Win q QEc ludL DECdlLlb
nouescent under the green light Of the
mercury lamp
Dr. Wood and professor Rubens
devised sort Of ray filter with which
they could separate the visible from
the invisible rays of light and with 1t
they were able to isolate the longest
heat wave ever discovered. It consists
OF box in which is imprisoned an
electric spark. The ultraviolet rays
of light from it are brought to a focus
upon small circular aperture upon a
cardboard screen, and the focal length
OF the lens is made so great that the
visible rays cannot come to a focus
at all. Held before the light white
paper was black, but when uranium
nitrate crystals We're substituted the
made manifest by the crystals shining
with brilliant green light
New Discoveries
Metallic mercury vapOr shines with
a brilliant light when exposed to the
invisible ultraviolet rays DR.. Wood
knew something of this, and in order
to determine the amount Of ABSORPTION
he sealed up a drop Of mercury in an
exhausted flask of quartz and To-
cussed the light of the mercury arc,
burning in a silica tube upon the
center of the bulb When the bulb
was Photographed with a quartz lens
the picture showed a cone Of focused
rays. precisely as If the bulb were
filled with smoke This is another
very good example of how new dis
coveries may be made by ultraviolet
photography.
Many remarkable conditions are re-
vealed when invisible light photographs
are made. The usual method of shut