The true northerner. [volume] (Paw Paw, Mich.) 1855-1920, 1876-08-11
THE MOON.
sonsafths Faxnrite Iunnr Studies.

Some of the Favorite LuDaS studies.
There are two lunar spots which the
selenographer regards with special favor,
because of the evidence they seem TO
give of change. One is crater lying on
the So called Sea of Serenity, which some
popular lunar observers regard as the
left eye Of the Man in the Moon. Here
there was once q deep crater nearly
seven miles across, very distinct and
obvious feature even with the small tele-
scope Oess than four inches in aperture)
used by Beer and Nader in forming
their celebrated chart. But, ten
years ago, the skillful astronomer
Schmidt, q selenographer of seleno-
graphers-who has, in fact, given the
best energies of his life to gazing
found this crater missing. When he
announced the fact to the scientific
world, other astronomers, armed with
very powerful Instruments, looked
for the crater which had been so
clearly seen with Madler's small
telescope; but, though they found a era
ter, it was nothing like the crater des-
cribed by Nader. The present crater
is scarcely two miles in diameter, and
only just visible with powerful telescopes;
all around it there is shallow depres-
sion, occupying region about as large
as the whole crater had been before. 1t
seems impossible to doubt that a great
change has taken place here, and the
question arises whether the change has
been produced by volcanic activity or
otherwise. Sir John Herschel pro-
nounced somewhat confidently in favor
of the former hypothesis. "The most
plausible conjecture" said he, Gas to
the cause of this disappearance seems to
be the filling up of the crater from be-
meath by an effusion of viscous lava,
which, overlooking the rim on
all sides, may have so flowed
down the outside slope as to eff
face its ruggedness. and convert it
into gradual declivity, casting no strong
shadows" But how tremendous the
volcanic energy required to fill with lava
a crater nearly seven miles in diameter,
and more than half mile deep The
volcanic hypothesis seems on this &C
count utterly incredible, for if such en-
ergy resided in the moons interior we
should find her whole surface contin-
ually changing. Far more probable
seems the idea that the wall of this era
ter has simply fallen in, scattering its
fragments over what had been the floor
OF the crater. The forces at work on
the moon are quite competent to throw
down steep crater walls like those which
seem formerly to have girt about this
deep cavity. Under the tremendous
and long lasting beat of the lunar mid
day sun, the rock substance of the
moons surface must expand. while dur
ing the intense cold of the lunar night
corresponding contraction must take
place. Under the influence of this al
ternate expansion and contraction the
strongest of the lunar crater-walls must
be tending to their downfall. Their
substance must be gradually crumbling
away. From time to time large masses
must topple over, and occasionally long
ranges of crater-wall must be brought
to the ground. 1t seems conceivable
enough, certainly far more probable
than any other Interpretation which has
been offered, that the crater-wall first
missed by Schmidt was destroyed in this
way. The other favorite region of sell
enographers is a much larger one-the
great walled plain called Plato, and by
the older astronomers the Greater Black
Lake, sixty miles in diameter, and sur
rounded by mountains, some of which
rise nearly $500 yards above the level
of the hoor.-SpectatOr.