Wood County reporter. [volume] (Grand Rapids [i.e. Wisconsin Rapids], Wis.) 1857-1923, 1886-07-15
WITHOUT SUNLIGHT.
Improvements by Which Photographs May be
Taken in the Dark

Improvements W WHICH IHOJOSrdpuS May Oc
Taken in the Dark
Capt. w. de Wyceleslie Abney, royal
engineers, F. R. s., has made remarkable
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 remarkably good
results. In trying different chemicals
In preparing his plate and developing 1t
he discovered combination which prov
ed sensitive to the heat rays in the spec
frum which are not visible to the naked
eye, and are located beyond the red of
the spectrum. This discovery is based
ON the theory that heat and light on the
same thing was further argument in
support of that theory. To illustrate:
radiant heat is light, if we could only
see it with the eve, and not merely dis
cetn with the mind, as we do, that it is
perfectly continuous in quality with the
species of radiant heat, which we
see with the natural eye through its eff
fectlng the retina with the sense of
light. Thus white-hot poker in a room
perfectly darkened from all other lights
is seen as brilliant whitelight, gradually
becoming reddish and less bright, until it
absolutely fades from vision in a dull red
glow. Long after 1T has ceased to be Wis
Idle to the eye, the fact that heat is being
radlcated from it is proven by our senses.
There Is a continuity throughc ut the pro-
cess, IN the first part of which the radiant
heat is visible, and in the second part in
visible to the human eye. We may sup
pose however, since we have plenty of IL
lustratlon'S In the animal kingdom of ewes
more sensitive in darkness than the hu-
man one, that some of them, say the cats
for example, can see the poker long after
1t has become invisible to the human
one.
This gave Capt. Abney his idea. and
since the camera Is an artificial eve he ar
guec that some plates might be obtained
which would be more sensive to the heat
rays than the ordinary PHOTOGRAPHIC
plate, which appreciates light only. Can't.
Abney experimental on the spectrum,
as being the most convenient method.
and after 1nnumeral attempts found that
the constituencies of plate coated with a
| special form of silver bromide. called by
him green" silver bromide in coIlodion,
and developed by ferrus oxalate, extended
Tar into the invisible part of the spec
trum. He accordingly prepared plate,
and, performing the simple expert
ment with the poker mentioned
above he exposed the plate at the instant
the iron became invisible to his eye. At
ter long exposure he developed his plate
and obtained an excellant photograph of
the poker. He then varied the experiment
by taking as an object teakettle of
water, the temperature of which was
gradually raised. His results in this case
were still better, and he obtained a series
of teakettle photographs 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 Sc
cluslon granted by dark nook in the
garden, and weep over the terrible perils
which will surround the loving young
couple of the future. The necessarily
long exposure also hampers the popu-
larity of the new process, but world
will get there.