Watertown republican. [volume] (Watertown, Wis.) 1860-1906, 1875-06-30
ASTRONOMICAL DISCOVERIES.

ASTRONOMICAL DISCOVERIES.
The Sun Not So far Away as Heretofore
Taught-Mechanical Force of Light.
From the New York Times.
The year 1875 seems likely to be dis
tinguished in the annals of astronomy
for the new evidence it is perfecting of
two important facts, both of which have
been held probable but have hitherto
lacked complete demonstration. The
first of these facts is that we are some
4 100000 or 100000 of miles nearer
to the sun than we had been taught by
our old text books on astronomy to be-
lieve, and thatconsequently the distances
OF all the planets from the sun and from
each other require to be calculated over
again and set down at much lower
figures. The evidence which the re-
cent observation of the transit of Venus
nave contributed to this important sub
ject is well known to our readers, and
is brought forcibly to mind by the re-
cent return of the Swatara to New York
with the transit expedition. The second
OF the demonstrations we have referred
to is that of the motive force of light.
At meeting of the Royal Society of
Great Britain, few weeks ago, Mr..
William Crookes, Fellow Royal Society,
who had previously communicated some
interesting facts on this subject, read
paper which may give rise to much
more important discoveries perhaps
than any contribution to Celestial me-
chanics since the law of gravitation was
demonstrated by Newton.
It has always been assumed, and DIR.
Balfour Stewart and other authorities
have affirmed, that light, apart from
heat, has no mechanical force whatever.
This old theory is overthrown by Mr..
Crookes, who for some years past has
been making experiments, and has at
last constructed an ingenious apparatus,
by which he shows the power of Ium1-
nous rays to drive round and round
little vane when the heat rays are ex-
Guided, being thoroughly sifted out by
means of screen of alum. We abridge
from the London Telegraph the follow
ing account Of one Of the experiments,
and regret that our space does not allow
more extended notice of the phenom-
ena submitted to examination before
the Royal Society. With an air pump
Mr.. Crookes first exhausts tube with
a bulb at it's end and in the bulb he
mounts upon a delicate pivot little
vane of glass or straw. This vane is
made in the form of the letter Y. and
on each of it's four arms is mounted a
disc of pith blaekened on one side.
The use of this blackened surface is in
genious, as will be presently seen. AS
soon as the machine isready, it is expos
ed to the sunshine, when it's discs imme-
diately become endued, as it were, with
life. They revolye around their common
axis just as the planets reyolve about
the sun in the orrery. What is the
motive force in this beautiful expert
ment (? It is not heat; for, as before
observed the heat rays can be sifted
out by the alumni screen without stop
ping the motion of the machine. The
atmosphere and it's changes have moth
ing to do with producing the motion.
Professor Osborne Reynolds some time
ago suggested that the disks revolved
because there was latent moisture in
them which, being evaporated in the
experiment, gave resilient impulse to
the little orrery. To refute this theory,
and, at the same time, to show that the
sole motive force engaged In driving
the orrery was the luminous rays of the
sun, Mr.. Crookes exhibited q machine
made wholly of platinum, which had
been heated to redness while under con-
tinuous and absolute exhaustion. The
discs being made of platinum, instead
of pith, as before, reyolved as obedi-
entity as the ,disks of piths. Inasmuch
as they could contain no appreciable
amount of latent moisture, the theory
of Professor Reynolds was, of course,
exploded.
The final result was that light is now
acknowledged for the first time as one of
themechanical forces, and such eminent
men as Professors Stokes and Huxley,
DR.. Carpenter, Mr.. Norman Lockyer
and others agree that the demonstration
was perfect