Evening star. [volume] (Washington, D.C.) 1854-1972, 1893-06-10
MAKEUP OF THE MOON.
Points on q New Theory About the Orb That
Sails at Night.


Points on q New Theory About the Orb That
Sails at Night.
VNHE THEORY THAT THE MOON Is
Il made Of green cheese was exploded quite q
little while ago. OF late years scientific per-
sons have been studying the satellite most at
tentively through telescopes and have formed
several rather contradictory notions respecting
it. One Of the most advanced ideas on the
subject is held by Prof. G. K. Gilbert Of the
geological survey He believes that the lunar
orb is made up Of ever SO many little moons
which once upon q time focked about the
earth.
Prof. Gilbert says that the side of the moon
visible from the earth is better mapped than
is the continent Of North America. 1t is of
Justabou the same size. The surveyor, looking
through the most powerful telescope, is still
several hundred miles away, and SO his map
does not represent the smallest features. On
the other hand, as all parts are equally accessi-
BILE, there is no region remaining unexplored.
The map Of the moon shows a number Of
great plains with dark floors: also a score of
mountain chains and a few trough-like valleys
remarkable for their s.raightness There are
likewise several thousand circular bowl shaped
cavities. which most observers have considered
to be craters of extinct volcanoes. These
craters have usually a circular rim of cliffs.
which rise to height of 5000 to $1,000 feet.
sometimes there is hill rising out of the
middle. There are from &c, 600 to 80 600 such
craters visible to the eye with the aid of first
rate telescope.
This would seem to be an astonishing num-
Der OF volcanic craters for small an area. In
North America, with about the same extent Of
surface, the remains of only about 5000 vol
canoes are found. At the same time, the great
majority OF such remains this continent
have been wiped out or buried by geologic
changes. 1t is probable that every part of the
United States, Canada and Mexico has had act
i've volcanoes at one time or another. The
craters might now be as numerous those on
the moon it there had been neither water nor
air to attack them.
The craters on the moon are enor-
mously bigger than any on the earth.
The largest one on this globe has a
diameter of fifteen miles. But this is pigmy
compared with the biggest lunar crater, which
measures 800 miles across. However. the cliffs
which define the edges OF volcanic craters are
composed of material thrown out from the
vent. lnasmuch as the attraction OF gravitation
on the moon is only one-sixth as strong as on
the earth, bombs Of given size and substance,
having the same initial velocity, would fly six
times as far, and the cliff formed of them
might stand six times as tall So a lunar crater
might be six times as broad and six times
wonder. The biggest craters on the moon
range from 5000 to Is, 900 feet in depth; those
on the earth from 1000 to 1000 feet.
NOT VOLCANIC cRATERs.
But Prof. Gilbert and those who coincide
with his thinking on this subject are confident
that the bowl-shaped cavities on the surface of
the moon are not volcanic craters. In fact, they
reject this idea altogether, conceiving it to be
untenable on grounds too deliberately scientific
for brief quotation here. According to their
opinion these peculiar features Of the lunar
landscape were originally produced by the i'm
pact OF little moons which struck the orb OF
night IL any projectile be made to hit q
plastic body with suitable velocity the scar pro-
duced by the shock has the form OF a crater.
With the right sort Of material, size of pro-
jectile and velocity Of impact, such a crater
may be made to have a central hill
So, according to this belief. il Is necessary to
consider the moon a body formerly bonn
barded by projectiles That the latter might
have been fired by terrestrial volcanoes was at
one time suggested. but the notion hat such
bombs could fly far enough to get beyond the
limits OF the earth's attraction is regarded as
absurd. The fact is conceived to be that the
projectiles in question were actually moonlets
OF greater or less dimensions, which ages ago
may have surrounded the earth in swarms 1t
Is imagined that there was a ring of small
moons, which finally broke up. The present
lunar orb happened to become center of ag-
gregation. Thus, having gone into the bust
ness OF collecting moonlets. 1t grew in mass
until 1t attained its present dimensions. The
earth also was SCARED all over by moonlets
which struck it, but the marks have been oblit-
Grated by the processes which continually recon-
struct and remodel the surface of the planet
AT length all Of the moonlets were absorbed
in the manner described. BY the earth and
moon. But the terrestrial planet is still SUBJ
jected to a continual bombardment with small
projectiles. 1t is reckoned that no less than
400 600 meteorites are captured by this
globe In the course of twenty-four hours. So
minute are most of them that being burned up
in collision with our atmosphere, their ashes do
not contribute to the surface Of the earth an
appreciable layer of dust But few are SO
big as to fall to the ground without being con- |
sumed, weighing from pounds to tons. They |
strike the atmosphere with a velocity far |
higher than could be induced by the earth's |
attraction. and it must be that they are speed |
ing through space in all directions in numbers |
that defy imagination. Their average velocity |
is about forty-five miles q second.
One Of the great plains on the moons surface |
is called the Mare lmbrium. The hills and fur |
rows in its neighborhood are all softened to the
ing landscape look as though it had been over |
spread with a layer Of semi-iquid matter. This |
is believed to have been the case. Once upon a |
time the moon at this spot is imagined TO have |
peen struck by a moonlet 50 or lOo miles in |
diameter The result was the generation of an |
enormous heat. which melted the greater part |
of the gigantic projectle instanter. Thus a |
defuge of semi-liquid material poured over |
the surface of the lunar satellite. reaching
for several hundred miles in all directions The
small craters it obliterated while it partly filled
up some of the larger ones. At the same
time solid fragments of the moonlet were scat
tered about. some of them flying 1000 miles
through the air and then scoring out burrows
from the moons surface as wide and deep as
the Grand Canyon of the Colorado. One of the
burrows dug by such fragment is lS7 miles
long and from 10 to Is miles broad, with
depth of ii 900 feet.
How tn Srnnka q CiOur