The Portland daily press., 1896-07-11

| What Once Were Thought to be Lunar
Seas Are Known Now to be Great De-
pressions; Formerly Filled with Water
| Volcanoes and Imposing Mountains.
| (By Sir Robert Ball in Lowndes's Profess
sor of Astronomy. University
of Cambridge.)
Not withdrawing that the moon is co.
000 miles distant from the earth, it
would in some respects be hardly an ex-
aggaration TO assert that we are better
acquainted with the topography of eur
satellite than we are with that OF the
globe which forms our home. No doubt
| it may at once be admitted that with re-
spect to large portion of the moon,
jewellers on the earth ere necessarily in
total ignorance. 1t is a popularity of our
satellite that it manages its movements
in such manner as to withhold nearly
half of its surface from ever being in
spected. 1t follows that we have no
means of learning what is on the other
side Of the moon. I do not suppose,
however, that in these days any one be-
lieves that if We could see it we would
find any characteristic difference between
the scenery on the remote side of the
moon and on the side which is turned
| toward the earth. So far, however, as
the neighboring globe Is displayed for
our observation, we can certainly assert
that there is hardly spot possessing the
size Of an ordinary parish which has not
been studied and photographed. sketched
by competent draughtsmen, duly laid
down on elaborate charts of the lunar
surface. and In many cases received the
dignity of special name. The ciroum-
stances Of the moons situation render it
much easier for US to survey its scenery
than it Is 30 survey the scenery of any
other celestial body. For. in the first
place, the moon may be regarded as
quite close to the earth. In Comparison
with the distances by which we are sspa-
rated from the other heavenly objects.
The sun is nearly four hundred times as
far away as the moon; and that planetary
globe whose surface We have studied to
the greatest advantage-I mean, Of
course, Mars-is seven under the most
favorable conditions. still at a distance
from the earth which is not less than
ons hundred and forty times as great as
that of the moon. But besides its con-
parative proximity there Ia another cir
eumstance which renders 1t comparative
ly easy for us to study the features on
our satellite. II globe like the earth in
size, as we'll Us in other particulars, had
been situated at the same distance from
us as that at which the moon now re-
wolves, it seems quite possible that we
should never have been able to obtain
any clear notion as to the geography of
such globe For our earth is. of course,
surrounded by thick coat of atmos-
phere; this atmosphere is at all times,
and in all parts, more or less opaque from
the presence of large quantities of float
Ing material while there are always some
regions where there is temporarily COM
plete obstruction, from the presence of
clouds. The atmosphere would thus op-
pose great difficulties to the study of the
geography of our earth by an outside
observer. 1t may, indeed. be well doubt
|
tinents could be completely disoerned,
notwithstanding that the area of the
earth az the distance of the moon would
be thirteen times larger than that of the
moon as presented to us.
For the purpose of the terrestrial as
tronomer, it fortunately happens that
the moon is almost entirely destitute of
atmosphere. The features of its surface
are consequently never obscured by any
Of those causes which would tend to hide
! the features of the earth from outside
scrutiny. Whenever the clouds on our
globe are out of the way, it is then pos
sible to observe the moon with but little
obstruction. II we also remember that
many of the features Of our satellite are
within reach Of a telescope of compare
lively moderate power, it will not be sur
prising that the lunar scenery has at
traoted so much attention and that thous-
ands of minute features on its surface
have been carefully identified. In some
cases, accomplished observers have deyot-
ell themselves with praiseworthy as
siduity to the detailed exami n alton Of
special parts on the surface.
| 1t would be impossible to enumerate
all the astronomers of recent times whose
labors have been directed to the study of
the lunar scenery. I may, however, here
mention'n few Names adding the remark
that there are doubtless many others
| whose valuable labors could not be
overlooked if 1t had been possible to give
more complete account of the subject
than would be practicable within the
limits Of the present article.
First, must mention Mr.. Nasmyth,
| who was at once a famous mechanical
engineer, q skilful artist and a devoted
student of the stars. He employed his
well-earned leisure i'll the study Of celes-
tial objects, and be devoted especial Rt-
tention to the moon. The work which
he produced in conjunction with Mr.
Carpenter is a standard authority on the
lunar scenery, and ia perhaps one Of the
most beautifully illustrated books that