Year: 1877




garded to all intents and purposes
dead, it must not be supposed that
no changes whatever take place
upon her surface. On the contra
ry, some Of the peculiarities of the
moons condition must tend to
cause even more rapid changes of
certain orders than take place in
the C sc of our own earth. Thus
the great length Of the lunar day,
and the moons waterless condition
and rare atmosphere, must help to
cause a comparatively rapid crum-
bling Of the moons surface. Dur
ing the long and intensely hot lunar
day the rock substance of the
moons surface must expand con-
siderably, for it is raised to degree
of heat exceeding that of boiling
water. During the long lunar
night the surface is exposed to a
degree Of refrigeration far exceed
ing that Of the bitterest winter in
the arctic regions, and must con-
tract correspondingly. This alter
nate expansion and contraction
must gradually crumble away all
the loftiest and steepost portions
0f the moons surface, and will
doubtless in the long run-that
is, some few hundreds of millions
of years hence = destroy all the
most most marked irregularities OF
the moons surface. The cases Of
change which have been recognized
by teleScopists who have carefully
studied the moons surface may all,
without exception, be referred to
this process Of gradual, but steady
disintegration. The most remark
able case hitherto known, for ex-
ample, the disappearance of the
lunar crater Lime, is far better ex-
planned in this way than as the re-
suit Of volcanic outburst. This
case has recently been described as
follows by the present writer: In
the lower Sea of Serenity there was
once a deep crater, nearly seven
miles across, a very distinct and
obvious feature, even with the small
telescope Qess than four inches in
aperture), used by Beer and Mad
ler in forming their celebrated
chart. But ten years ago the as
trOnomer Schmidt, a selenographer
of selenographers (who has in fact
given the best energies of his life to
moon-gazing), found this crater
missing. When lie announced the
fact to the scientific world, other as.
tronomers armed with very power
full intruments looked for the crater
which had been so clearly seen with
Madlel's small telescope; but
though they found crater, it was
nothing like the crater described
by Madler. The present crater is
scarcely two miles in diameter and
only Just visible with powerful
telescopes; all around it there
is shallow depression, occu-
pying a 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 vol
canic activity or otherwise. Sir
John Herschel pronounced some
what confidently in favor of the
former hypothesis. The most
plausible conjecture" said he, "as
TO the cause Of this disappearance
seems to be the filling up of the
crater from beneath by an effusion
of vicious lava, which, overllowing
the rim on all sides, may have 80
flowed down the outer slope as to
eflace its tsruggedness, and convert it
into a gradual dcclivity casting no
stray shadows" "But how tremen-
dous the volcanic energy" we note
in the passage referred to, Z" re-
quired to fill with lava a crater
nearly seven miles in diameter and
more than half mile deep? The
volcanic hypothesis seems on this
account utterly incredible, for if
such energy resided in the moons
interior we should find her whole
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