The Republican. [volume] (Oakland, Md.) 1877-current, 1892-01-15
STARS BEYOND SIGHT.
The Importance of the Photographic Plate
In Astronomy.

|
In Astronomy.
When the air is damp and warm q
new iron surface will corrode very
quickly. Exposure for a single day is
enough to mark nail here and there
with specks of rust, easily removed by
touch. However closely one might
observe the nail from the first moment
of its exposure, it would be impossible
to see the change taking place in it's
color The eye would tire of watching
long before a grain of rust would come
into view. An example this of count
less forces of nature too gradual in
their activity to come within the limits
during which the eye can sustain it's at
tention. They require time, and often
a very long time.
Now, if instead of the eve, so feeble
and so easily fatigued, we have some
thing moro sensitive to light and not
subject to WEAKNESS, we can at once in
directly and very greatly extend the
field of human vision. Such n substi-
tute is found in the Photographic plate
when it is treated with newly devised
compounds, upon which rays too faint
to be otherwise detected can imprint
themselves.
Besides its exquisite responsiveness
to light, this plate has another ndvan-
tage over the eye We may look direct
ly Mt distant star, but II its ray is too
weak to excite vision, our gaze is in
vain. no matter how long we may be
able to maintain IT, Not SO with the
plate. The rays which fall upon IL,
however faint they may be, steadily in
crease their effect from minute TO min
ute, from hour to hour, until at last
they yield a perfect distinct image.
All this has been applied in awonder-
full way to the study of the heavens.
With every successive improvement in
the power of telescopes, astronomers
have brought into their ken nebulD
and stars before unseen.
They know that invisible stars must
far outnunber the visible ones, for the
whole volume of starlight is much
greater than the beams received from
the stars within the telescopes range.
Their belief, based upon past observa-
ton, is that space beyond vision is ever
ready to reveal new wealth of worlds
to any new power OF exploration.
Precisely such power is conferred
by the sensitive plate just described.
When it is attached to n telescope,
whose lenses are by suitable mechanism
kept constantly directed at particular
point in the sky, the astronomer is able
vastly to extend the diameter of the
visible universe. Orbs so remote, or SO
fee BILE in their ray, as to be invisible to
the l1ecnest observer, in the course of n
clear night form well-dcfined picture
in the camera.
This noblest use Of light as Inner
has brought to view a sphere Of crea-
ton which no mortal eye shall ever di-
rectly see, sphere thclxly gemmed with
stars, and stars in the malling--as we
now know nebulie to be.
BY a subdivision of the heavens
among the worlds chief observatories,
comprehensive mapping Of the skies
is now in progress. 1t will be much
more accurate and full than any previ-
Gus work of the kind.
In securing pictures of particular
heavenly bodies photography is quite
as important as in making charts of the
stars. Prof. +. ). Holden. who has
charge of the great Lick telescope at
Mount Hamilton, California declares
that the camera in forty minutes has
given him as much knowledge of the
moons surface as he has been able to
obtain in four years observation.
The satellite of Neptune, though in
visible in the telescope on account of
its proximity to the planet, has been
photographed in every part of its orbit.
What wielder OF the pencil or the
brush would have dared to transfer the
suns lineaments to paper or canvas? 1t
was reserved for the photographer, by
fine stretch of audacity, to compel the
sun TO take his own portrait, and to 90
it in the fraction of second. Youths
Companion.