Evening star. [volume] (Washington, D.C.) 1854-1972, 1911-03-26
Meteors and Light

MeCeOf9 an0
HOW many know that the earth is getting
IL larger each year from the fall of meteoric
matter on its surface, and that such matter
is of no small weight? One hundred tons
day is the estimate made by Young. This,
he says, would make layer one inch thick
over the entire earth in one thousand million
years, if we assume this meteoric matter to
be three times as heavy as water. But an
other 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 keeping us away
from the sun gets much greater too, and IN
fact more so than the suns gravity, the re-
suit 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 announced: The light received from
star of the first magnitude like Vega is about
one Observation-Disclosures Of the suns.
Young places the total starlight received by
the earth at the value of three thousand first
magnitude stars, thus making the whole star
light 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 force some
thing like seventy thousand tons. AS the
surface of a sphere varies as the square OF
the radius, and as the volume or mass varies
as the cube of the radius, and as the mechan-
ical pressure of light on the whole surface
varies as that surface, and as the force of
gravity varies as the mass,-lf 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 a certain minuteness could not reach
the sun, but would be repealed by the me-
chanical force of its light.
A Big Marine Light
A N example of the immense increase in the
"A power of modern marine lights is fur
nished by the equipment of the St. Cathe-
rines Lighthouse on the south coast of the
Isle of Wight. 1t has power of fifteen mill
ion candles, as against the three million can
dlepower of the light it replaced. The later
lens throws three distinct beams of light,
which follow one another across the water.
The apparatus revolves in trough of mer
curry, on which it is foated, instead of being
carried by rollers as hitherto. Over eight
hundred pounds of mercury is required to
fill the trough.
The Searchlight's Beam
NEARLY everybody is familiar with the
~ beam of searchlight, and knows why
the beam is visible while lightitself cannot
be seen unless it strikes the eye, its visibility
being due to particles in the air which really
do reflect the light to the eye. On 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 fading away into nothing, as it
does pointed horizontally on 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 its 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 horizon
tally whether the fog is universal or occur
ring only in patches; for, if extending to
great distance, the beam gradually gets
DINNER and DINNER, but if in patches the
beam is lighter in patches, and if it goes
through place with no fog at all that part
of the beam is black or invisible.
Why the Ta1low Dip
WIN &c r. +bo+ tho morn a1actr,o 1;ohfc