Grant County herald. [volume] (Lancaster, Wis.) 1850-1968, 1875-07-08
AN ASTOUNDING SCIENTIFIC DIS
O0VERY.
The Mechanical Force of Light Dem onstrated
The Greatest Discovery Since That Of the
Law Of Gravitation.

The Mechanical Force of Light demonstrated
The Greatest Discovery Since That Of the
Law OF Gravitation.
1t has always been assumed, and
the highest authorities have affirmed,
that light, apart from heat, has no
mechanical force whatever. But at
recent meeting of the Royal Society
of Great Britain, Sir William Crookes,
a Fellow of that Society, read pa
per detailing experiments of his own,
demonstrating the mechanical power
of luminous rays-a discovery likely
to prove as important to science as
any since the demonstration of the
law of gravitation. Mr.. Crookes first
procures tube with a bulbe at the
end. In the bulb he mounts on a very
delicate pivot a little vane of straw
or glass; or rather two vanes, cross
ing at the pivot, in the form of the
litter x. On each of the four arms
is mounted disk of pith-blackened
on one side, for purposes to be made
plain hereafter. Then, with an air.
pump, he thoroughly exhausts the
tube-so that there shall be no air to
prevent or retard the revolution of
the vanes, in case of the application
of any power tending to move them.
The machine is now exposed to the
sunshine-the black discs possessing
black more power of absorbing rays
of light than any other COLOR being
set so as to face the sunlight I'm
mediatel y the discs become apparent
ly endued with life, and revolve swift
ly about their common axis, like plan
in an orrery. What is the motive
force in this experiment Not the
atmosphere nor changes therein, for
it has been carefully excluded. Not
the suns heat, for the heat.rays can
be sifted out by an alum screen with
out stopping the rotation of the orrery.
Prot Osborn Reynolds suggested the
r.fetched theory that the discs re.
volved because there was a latent
moisture in them which, being evapo-
rated in the experiment, gave a re-
silent impulse to the little orrery. To
refute this theory, Mr.. Crookes in
vented machine, which, including
the discs, was made wholly of platin-
UNI which had been heated to redness,
while under continuous and absolute
exhaustion; but the discs revolved as
obediently as though made of pth.
Inasmuch as there could be no "latent
moisture" in them under such circum-
stances, Prof. Reynolds theory was
exploded. Whenever and under
whatever circumstances the waves of
light are allowed to dash themselves
against the black disc of the orrery
they drive it before them. Shut off
the light by standing between the
orrery and the sun, and the rotation
ceases as soon as the momentum is
overcome-to be renewed the mo-
ment light is re-admitted. If a cloud
passes over the face of the sun while
the little orrery is working at full
speed, its movements are checked and
somewhat slower, but the moment the
sun is visible again the mechanism re-
spends with alacrity, and its revolu-
tions are as swift as ever
Mr.. Crookes stands in the front rank
of scientists. To him science owes
the discovery of the metal thalium,
and the complete establishment of its
atomic weight, and many other sug-
gestions of value owe their origin to
him. This demonstration that light
is mechanical force is one of the
highest scientific Importance, if con-
firmed-and Profs. Huxley, Stokes,
DR.. Carpenter, Mr.. Norman Lockyer,
and others eminent in science, affirm
that the demonstration is perfect, thus
revealing to the eye of man for the
first time one of the most occult, yet
all-pervading and powerful forces of
nature. The subtlest of the known
imponderables is set to turn a wheel
like willing slave. Calculating from
the small surface of these discs of pith
the motive force of sunlight, ere long
our mathematicians will be telling us
the aggregate power of the luminous
rays of the sun. Here is the rule of
three for the simple yet enormous cal
culation As the surface of quar-
terinch disc Of pith, is to the surface
of spere whose radius is the earth's
distance from the sun, so is the power
exerted upon the little disc to the to-
tai power exerted at the earth's dis
lance. And by the law of forces
nothing of this can be wasted or lost.
Less than one-2, 100000, 000ths part
of the whole is intercepted by our
own globe, to transform it into a
thing of beauty; about one-2,000, 00O,-
000th part of the rest is utilized by
the other planets and satellites of our
system; but incalcuably the greater
part escape into free space to perform
some work concerning which we as
yet know nothing. Here is a field of
investigation upon whose confines we
stand-who knows how near the
verge of new and still more astound-
ing discoveries? s'Let there be light
and there was light" derives a ne W
majesty of meaning from the discov-
cry which shows this subtle something
to be no mere undulation and mode
of motion, not only the illumination of
all life, but itself an infinite living
force.
THE BRIDGES OF THE WEST
Nothing excels in wonder the bridge