The Rutland daily globe. [volume] (Rutland, Vt.) 1873-1877, 1875-06-11
The 8utland daily Globe
FRIDAY, JUNE II. 1875.
Two Astronomic Discoveries.

hSiu piOOhblC DuL ntNC nllDtTlO iHChtu
complete demonstration. The first of these
facts is that we are some 100000 or
5,000,000 of miles nearer to the sun than
we had been taught by our old textbooks
on astronomy to believe and that conse-
quently 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 recent observations of the transit
of Venus have contributed to this inn
portant subject is well known to our read
ers, and is brought forcibly to mind by the
recent 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 a paper which
may give rise to much more important dis
coyeries perhaps than any contribution to
Celestial mechanics since the law of gravi-
taton was demonstrated by Newton. 1t
has always been assumed, and DR.. Balfour
Stewart and other authorities have affirmed,
that light, apart from heat, has no me-
chanical force whatever. This old theory
is overthrown by Mr.. Crookes who for
some years past has been making expert.
ments, and has at last constructed an in
genious apparatus, by which he shows the
power of luminous rays to drive round and
round little vane when the heat rays are
excluded, being thoroughly sfted out by
means of screen of alum. We abridge
from the London Telegraph the following
account of one of the experiments, and re-
greet that our space does not allow more
extended notice of the phenomena submit
ted to examination before the Royal socie-
! ty. With an air pump Mr.. Crookes first
exhausts tube with little vane of glass
or straw. This vane is made in the form
of the letter X, and on each of its four
arms is mounted disc of pith blackened
on one side. The use of this blackened
surface is ingenious, as will be presently
seen. AS soon as the machine is ready, it
is exposed to the sunshine, when its discs
Immediately become enbued, as it were,
with life. They revolve around their com
mon axis just as the planets revolve about
force in this beautiful experiment ? 1t is
not heat. For, as before observed, the
heat rays can be sfted out by the alum
screen without stopping the rotation of the
machine. The atmosphere and its changes
have nothing to do with producing the mo-
ton. Prof. Osborne Reynolds some time
| ago suggested that the discs revolyed be-
cause 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 ex-
hibited machine made of platinum which
had been heated to redness while under
continuous and absolute exhaustion. The
discs being made of platinum instead CT
pith, as before, revolved as obediently as
the discs of pith inasmuch as they could
contain no appreciable amount of latent
moisture, the theory of Prof. Reynolds
was, of course, exploded. The final result
was that light is now acknowledged for the
first time as one of the mechanical forces,
and such eminent men as Profs. Stokes
and Huxley, DIR. Carpenter, Mr.. Norman
Lockyer, and others, agree that the demon.
stration was perfect.
Another point of importance is that the
force which light delivers is not like the
force of gravitatlon, but differs from it in
several essential respects One of these 10,
that while gravitation attracts and gives a
centripetal impulse the force of light is
centrifugal, and repels or pushes away the
objects on which it is delivered. Thus the
black side of the disc is pushed from the
sun. and the orrery of Mr.. Crookes is kept
in constant rotation so long as the light
waves dash themselves against the black
surface and drive it before them chem.
Shut out the light by covering the machine
with hat, and the rotation instantly stops,
to be renewed again the moment the OBJ
struction is taken away and the light read
mltted. A blue or green screen diminishes
the force of the rotation. Yellow or red
glass quickens it into much more lively
activity. 1T cloud passes over the face
of the sun while this little orrery is work
ing at full speed its movements are check
cred and somewhat slower, but the mo-
ment the sun is visible again the mechanism
responds with alacrity, and its revolutions
are as swift as ever.
Mr.. Crookes is well-known as the man
to whom science owes the discovery of the
metal thallium, and the complete establish
ment of its atomic weight. He has also
invented the radiometer. But the little
orrery we have described above is a much
more remarkable continuance. Ii contains
the promise of further discoveries. 1t will
perhaps raise its inventor to the front rank
among the explorers of physical science.
In this simple little machine one Of the
most occult forces of nature is for the first
time revealed to the eye of man. In 1t,
says the authority from which the fore
going facts are chiefly taken, 1--WE see the
subtlest of imponderables set like a willing
slave to turn a wheel ; while tiny as that
wheel is in these experiments, we must re-
member that hight pervades it, flashing per-
petually from countless centers like our
own sun, across the Infinite ether, and it
may be fairly imagined that the lnterplane-
tary ether resembles the vacuum in the
bulb, so that the condition of these revolv-
ing discs is, perhaps, much the same as
that of the planets in space. Strange, in
deed, are the thoughts which must be
started by this revelation that light, pour
ing upon bodies freed from atmospheric
friction, is in itself an active and mighty
force. That so remarkable discovery solves
at once the mystery of the comets tall
which is always seen to he driven violently
away from its natural line upon approach.
ing the SUMS, we believe, affirmed by
more than one high astronomical authority.
But may it not also have something TO dc
with the axal motion of the planets? May
it not have something to do with the main
tenance OF centrifugal force, balancing, as
1t were, that of gravitation ? Can 1t be
for nothing in the celestial universe that
this potency and stress Of light sweeps
from centre to circumference of each sys-
tenn, exercising a power which, in Its to-
tality, must be something prodigious IL
seems not impossible that our mathemati-
clans, calculating from the small surface
of these discs the motive force OF sunlight,