The Black Hills union and western stock review. [volume] (Rapid City, S.D.) 1904-19??, 1911-03-31
Many QUEER FACTS
CONCERNING LIGHT
Very Few Know That the Earth Is
Getting Larger Each Year.

| getting larger each year from the
lall of meteoric matter on its sur
| face, and that such matter is of no
small weight? One hundred tons
day is the estimate made by
Young. This, he says, would make
a layer one inch thick over the en-
tire earth in one thousand million
years. If we assume this meteoric
matter TO be three times as heavy
as water But another effect has to
take place at the same time; as the
earth is getting larger the force OF
gravity gets larger, and we are being
attracted with more force toward the
sun; but the centrifugal force keep
ing us away from the sun gets much
greater too, and in fact more so than
the suns gravity, the result being
that we are gradually increasing our
distance from the glowing orb
Starlight has been measured in
comparison with the sunlight, and
the following results been announc-
ed: The light received from a star
Of the first magnitude like Vega is
about one forty-thousandth-m illionth
of the suns. Young places the to-
tai starlight received by the earth
at the value of three thousand first
magnitude stars, thus making the
whole starlight to be one-sixtieth
that of the full moon
Light has an actual mechanical
pressure and can be measured in
the laboratory. 1t has been found
that the suns light in itself presses
against the earth with a force some
thing like seventy thousand tons. AS
the surface of a sphere varies as the
square Of the radius, and as the VOL
ume or mass varies as the cube of the
radius, and as the mechanical pres
sure Of light on the whole surface
varies as that surface, and as the
force of gravity varies as the mass
If a sphere was made smaller and
smaller it is easily seen that the
pressure Of light does not decrease
so fast as the force Of gravity; SO
bodies beyond certain minuteness
could not reach the sun, but would
be repealed by the mechanical force
of it's light.
An example of the Immense in
crease in the power of modern mar
inc lights is furnished by the equip
ment Of the St. GATHERINGS Light
house on the south coast of the Isle
of Wight. 1t has power of fifteen
million candles, as against the three
million candlepower of the light it
replaced. The later lens throws
three distinct beams of light, which
follow one another across the wa
ter. The apparatus revolves in q
trough Of mercury, on which 1t 10
foated, instead Of being carried by
rollers as hitherto. Over eight hun
dred pounds of mercury is required
to fill the trough.
Nearly everybody is familiar with
the beam of a searchlight, and knows
why the beam is visible, while light
itself cannot be seen unless it strikes
the eye, it's visibility being due to
particles in the air which really do
reflect the light to the eye. On a
foggy night, If one will notice, the
beam seems to come abruptly to an
end if the light is pointed upward.
1t does this instead of gradually fad
ing away into nothing, as it does
pointed horizontally on a uniformly
foggy night.
The thing is rather puzzling to one
first seeing it; but the reason is not
far to seek. Where the end of the
beam seems to be there is the place
the fog ends; for the beam cannot
be visible to us unless there are
small particles in it's path. This is
of great help to sailors in judging
OF the state of the weather; for they
can tell exactly how thick the fog is,
or rather how deep it is. They can
also tell by throwing the light hori-
zontally whether the fog is univer-
sal or occurring only in patches; for
if extending to a great distance, the
beam gradually gets DINNER and
DINNER, but if in patches the beam
is lighter in patches, and if it goes
through a place with no fog at al
that part Of the beam is black OF
invisible.
Why is it that the more electric
lights there are, and the more kero
sene burned, the greater is the de
mand for old fashioned wax and
tallow candles? So popular, indeed
is the ''tallow Dip that the factor
les of this country annually consume
some one hundred and thirty millioi
pounds of material in turning gu
the tapers. In London there is {
candle factory that extends over fiji
1 - Il h