Little Falls transcript. [volume] (Little Falls, Morrison County, Minn.) 1876-1894, 1886-07-23
: u, ~ ~; s.zii ~ Il - 3.
WITHOUT SUNLIGHT.
improvements by Which Photo
graphs May be Taken In
the Dark

graphs May be Taken In
the Dark. .1
Capt. W. de Wyceleslie Abney, royal
engineers, F. r. S., has made remarka-
BILE discoveries in photography, and
much of the recent progress in the art
has been due to him. Capt. Abney
paid special attention to photographs
OF the solar spectrum, and had some
remarkable good results In trying
different chemicals in preparing his
plate and developing it he discovered
combination which proved sensitive to
the heat rays in the spectrum which
are not visible to the naked eye, and
are located beyond the red of the spec
trum. This discovery is based on the
theory that heat and light on the same
thing was further argument in sup
port of that theory. To illustrate: Ra-
diant heat is light, if we could only see
it with the eye, and not merely discern
with the mind as we do, that it is per-
fectly continuous in quality with the
species Of radiant heat which we see
with the natural eye through its affect
ing the retina with the sense of light.
Thus, white-hot poker in room per-
fectly darkened from all other lights is
seen as a brilliant white light, gradual
]y becoming reddish and less bright,
until it absolutely fades from vision in
dull red glow. Long after it has
ceased to be visible to the eye, the fact
that heat is being radiated from it is
proven by our senses. There is contin-
uity throughout the process, in the
first part of which the radiant heat is
visible, and in the second part invisible
to the human eye. We may suppose.
however, since we have plenty Of illus
trations in the animal ingdom of eyes
more sensitive in darkness than the HUI
man one, that some of them. say the
cats, for example, can see the poker
long after it has become invisible to
the human one.
This gave Capt Abney his idea, and
since the camera is an artificial eye, he
argued that some plates might be OBJ
tanned which would be more sensitive
to the heat rays than the ordinary pho
:ographic plate, which appreciates light
only. Capt Abney experienced on the
spectrum, as being the most conven-
lent method, and after innumcrable at
tempts found that the sensitiveness of
a plate covered with special form of
silver bromide, called by him green
silver bromide, in collodion, and dey-
eloped by ferrous oxalate, extended far
INTO the invisible part of the spectrum.
He accordingly prepared plate, and,
performing the single experiment with
the poker mentioned above, he exposed
the plate at the instance the iron be-
came invisible to his eye, After long
exposure he developed his plate and
obtained an excellent photograph of
the invisible poker. He then varied the
experiment by taking as an object
teakettle of water, the temperature of
which was gradually raised. His res
ults in this case were still better, and
he obtained series of teakettle photo
graphs almost as good as those taken
in the light.
This is the present stage of the game,
as the sporting editor would say, and
the time has not yet arrived when the
amateur photographer can go out and
photograph pussy on the back fence by
the aid of his animal heat radiations,
The loving couples of to-day can still
seek the seclusion granted by d dark
nook in he garden, and weep over the
terrible perils which will surround the
loving young couple of the future. The
necessary long exposure also hampers
the popularity of the new process, but
the world will get there.-PiNsburgh
Chronicle Telegraph.