EAST LONGITUDE 0 deg. TO 20 deg.
MURCHISON.--A considerable ring-plain about 35 miles across on the E.,
where it abuts on Pallas. It is a pear-shaped formation, bounded on the
N. by a mountainous region, and gradually diminishes in width towards the
S.E., on which side it is open to the plain. The walls are of no great
altitude, but, except on the N.W., are very bright. At the S. termination
of the W. wall there is an exceedingly brilliant crater, Murchison A,
five miles in diameter and some 3000 feet deep; adjoining which on the
N.W. is an oval depression and a curious forked projection from the
border. The only objects visible in the interior are a few low ridges on
the E. side, and a number of long spurs running out from the wall on the
N. towards the centre of the floor. Murchison A is named CHLADNI by
Lohrmann.
PALLAS.--A fine ring-plain, about 32 miles in diameter, forming with
Murchison an especially beautiful telescopic object under suitable
illumination. Its brilliant border, broken by gaps on the W., where it
abuts on Murchison, has a bright crater on the N.E., from which,
following the curvature of the wall, and just below its crest, runs a
valley in an easterly direction. There is a large bright central mountain
on the floor, with a smaller elevation to the S. of it, and a ridge
extending from the N. wall to near the centre. On the W., a section of
the border is continued in a N. direction far beyond the limits of the
formation; and on the S. it is connected with a small incomplete ring; on
the E. of which, near the foot of the wall, is a somewhat smaller and
much duskier enclosure.
BODE.--A brilliant ring-plain, 9 miles in diameter, situated on the N.
side of Pallas. Its walls rise about 5000 feet above the interior, which
is considerably depressed, and includes, according to Schmidt and Webb, a
mountain or ridge. There are two parallel valleys on the W., which are
well worth examination.
SOMMERING.--An incomplete ring-plain, 17 miles in diameter, situated on
the lunar equator. It has rather low broken walls and a dark interior.
SCHROTER.--A somewhat larger formation, with a border wanting on the S.
Schmidt draws a considerable crater on the S.W. side of the floor. It was
in the region north of this object, which abounds in little hills and low
ridges, that in the year 1822 Gruithuisen discovered a very remarkable
formation consisting of a number of parallel rows of hills branching out
(like the veins of a leaf from the midrib) from a central valley at an
angle of 45 deg., represented by a depression between two long ridges
running from north to south. The regularly arranged hollows between the
hills and the longitudinal valley suggested to his fertile imagination
that he had at last found a veritable city in the moon--possibly the
metropolis of Kepler's _Subvolvani_, who were supposed to dwell on that
hemisphere of our satellite which faces the earth. At any rate, he was
firmly convinced that it was the work of intelligent beings, and not due
to natural causes. This curious arrangement of ridges and furrows, which,
according to Webb, measures about 23 miles both in length and breadth,
is, owing to the shallowness of the component hills and valleys, a very
difficult object to see in its entirety, as it must be viewed when close
to the terminator, and even then the sun's azimuth and good definition do
not always combine to afford a satisfactory glimpse of its ramifications.
M. Gaudibert has given a drawing of it in the _English Mechanic_, vol.
xviii. p. 638.
GAMBART.--A regular ring-plain, 16 miles in diameter, with a low border
and without visible detail within; situated nearly on the lunar equator,
about 130 miles S.S.W. of Copernicus, at the N.W. edge of a very hilly
region. A prominent pear-shaped mountain, with a small crater upon it,
stands a short distance on the S.W., and further in the same direction, a
large bright crater with two much smaller craters on the N. of it. The
rough hilly district about midway between Copernicus and Gambart is
remarkable for its peculiar dusky tone and for certain small dark spots,
first seen by Schmidt, and subsequently carefully observed by Dr. Klein.
The noteworthy region where these peculiar features are found represents
an area of many thousand square miles, and must resemble a veritable
_Malpais_, covered probably with an incalculable number of craters,
vents, cones, and pits, filled with volcanic _debris_. It is among
details of this character that the true analogues of some terrestrial
volcanoes must be looked for. Under a low angle of illumination the
surface presents an extraordinarily rough aspect, well worthy of
examination, but the dusky areas and the black spots can only be
satisfactorily distinguished under a somewhat high sun. I have, however,
seen them fairly well when the W. wall of Reinhold was on the morning
terminator.
MARCO POLO.--A small and very irregularly-shaped enclosure (difficult to
see satisfactorily) on the S. flank of the Apennines. It is hemmed in on
every side by mountains.
ERATOSTHENES.--A noble ring-plain, 38 miles in diameter; a worthy
termination of the Apennines. The best view of it is obtained under
morning illumination when the interior is about half-filled with shadow.
At this phase the many irregular terraces on the inner slope of the E.
wall (which rises at one peak 16,000 feet above an interior depressed
8000 feet below the Mare Imbrium) are seen to the best advantage. The
central mountain is made up of two principal peaks, nearly central, from
which two bright curved hills extend nearly up to the N.W. wall,--the
whole forming a V-shaped arrangement. On the S. there is a narrow break
in the wall, and the S.W. section of it seems to overlap and extend some
distance beyond the S.E. section. The border on the S.W. is remarkable
for the great width of its _glacis_. Eratosthenes exhibits a marked
departure from circularity, especially on the E., where the wall consists
of two well-marked linear sections, with an intermediate portion where
the crest for 20 miles or more bends inwards or towards the centre. From
the S.E. flank of this formation extends towards the W. side of Stadius
one of the grandest mountain arms on the moon's visible surface, rising
at one place 9000 feet, and in two others 5000 and 3000 feet respectively
above the Mare Imbrium. If this magnificent object is observed when the
morning terminator falls a little E. of Stadius, it affords a spectacle
not easily forgotten. I have often seen it at this phase when its broad
mass of shadow extended across the well-known crater-row W. of
Copernicus, some of the component craters appearing between the spires of
shade representing the loftiest peaks on the mountain arm. There is a
prominent little crater on the crest of the arm between two of the peaks,
and another on the plain to the west.
STADIUS.--An inconspicuous though a very interesting formation, 43 miles
in diameter, W. of Copernicus, with a border scarcely exceeding 200 feet
in height. Hence it is not surprising that it was for a long time
altogether overlooked by Madler. Except as a known object, it is only
traceable under very oblique illumination, and even then some attention
is required before its very attenuated wall can be followed all round. It
is most prominent on the W., where it apparently consists of a S.
extension of the Eratosthenes mountain-arm, and is associated with a
number of little craters and pits. This is succeeded on the S.W. by a
narrow strip of bright wall, and on the S. by a section made up of a
piece of straight wall and a strip curving inwards, forming the S. side.
On the E. the border assumes a very ghostly character, and appears to be
mainly defined by rows of small depressions and mounds. On the N.E., N.,
and N.W. it is still lower and narrower; so much so, that it is only for
an hour or so after sunrise or before sunset that it can be traced at
all. On every side, with the exception of the curved piece on the S., the
wall consists of linear sections. The interior contains a great number of
little craters and very low longitudinal mounds. Ten craters are shown in
Beer and Madler's map. Schmidt only draws fifteen, though in the text
accompanying his chart he says that he once counted fifty. In the
monograph published in the _Journal_ of the Liverpool Astronomical
Society (vol. v. part 8), forty-one are represented. They appear to be
rather more numerous on the S. half of the floor than elsewhere. Just
beyond the limits of the border on the N., is a bright crater with a much
larger obscure depression on the W. of it. The former is surrounded by a
multitude of minute craters and crater-cones, which are easily seen under
a low sun. Though almost every trace of Stadius disappears under a high
light, I have had little difficulty in seeing portions of the border and
some of the included details when the morning terminator had advanced as
far as the E. wall of Herodotus, and the site was traversed by
innumerable light streaks radiating from Copernicus. At this phase the
bright crater, just mentioned, on the N. edge of the border was tolerably
distinct.
COPERNICUS.--This is without question the grandest object, not only on
the second Quadrant, but on the whole visible superficies of the moon. It
undoubtedly owes its supremacy partly to its comparative isolation on the
surface of a vast plain, where there are no neighbouring formations to
vie with it in size and magnificence, but partly also to its favourable
position, which is such, that, though not central, is sufficiently
removed from the limb to allow all its manifold details to be critically
examined without much foreshortening. There are some other formations,
Langrenus and Petavius, for example, which, if they were equally well
situated, would probably be fully as striking; but, as we see it
Copernicus is _par excellence_ the monarch of the lunar ring-mountains.
Schmidt remarks that this incomparable object combines nearly all the
characteristics of the other ring-plains, and that careful study directed
to its unequalled beauties and magnificent form is of much more value
than that devoted to a hundred other objects of the same class. It is
fully 56 miles in diameter, and, though generally described as nearly
circular, exhibits very distinctly under high powers a polygonal outline,
approximating very closely to an equilateral hexagon. There are, however,
two sections of the crest of the border on the N.E. which are inflected
slightly towards the centre, a peculiarity already noticed in the case of
Eratosthenes. The walls, tolerably uniform in height, are surmounted by a
great number of peaks, one of which on the W., according to Neison,
stands 11,000 feet above the floor, and a second on the opposite side is
nearly as high. Both the inner and outer slopes of this gigantic rampart
are very broad, each being fully 10 miles in width. The outer slope,
especially on the E., is a fine object at sunrise, when its rugged
surface, traversed by deep gullies, is seen to the best advantage. The
terraces and other features on the bright inner declivities on this side
may be well observed when the sun's altitude is about 6 deg. Schmidt,
whose measures differ from those of Neison, estimates the height of the
wall on the E. to be 12,000 feet, and states that the interior slopes
vary from 60 deg. to 50 deg. above, to from 10 deg. to 2 deg. at the
base. The first inclination of 50 deg., and in some cases of 60 deg., is
confined to the loftiest steep crests and to the flanks of the terraces.
There are apparently five bright little mountains on the floor, the most
easterly being rather the largest, and a great number of minute hillocks
on the S.E. quarter. S.W. of the centre is a little crater, and on the
same side of the interior a curious hook-shaped ridge, projecting from
the foot of the wall, and extending nearly halfway across the floor. The
region surrounding Copernicus is one of the most remarkable on the moon,
being everywhere traversed by low ridges, enclosing irregular areas,
which are covered with innumerable craterlets, hillocks, and other minute
features, and by a labyrinth of bright streaks, extending for hundreds of
miles on every side, and varying considerably both in width and
brilliancy.
The notable crater-row on the W., often utilised by observers for testing
the steadiness of the air and the definition of their telescopes, should
be examined when it is on the morning terminator, at which time Webb's
homely comparison, "a mole-run with holes in it," will be appreciated,
and its evident connection with the E. side of Stadius clearly made out.
There is another much more delicate row running closely parallel to this
object; it lies a little W. of it, and extends farther in a northerly
direction.
ARCHIMEDES.--Next to Plato the finest object on the Mare Imbrium. It is
about 50 miles in diameter. The average height of its massive border is
about 4000 feet above the interior, which is only depressed some 500 or
600 feet below the Mare, the highest peak (about 7000 feet) being on the
S.E. The walls are terraced, and include much detail, both within and
without. The most noteworthy features in connection with this formation
are the crater-cones, craterlets, pits, white spots, and light streaks
which figure on the otherwise smooth interior. Mr. T.P. Gray, F.R.A.S.,
of Bedford, who, with praiseworthy assiduity, has devoted more than ten
years to the close scrutiny of these features, Mr. Stanley Williams, and
others, have detected four crater-cones on the E. half of the floor, and
about fifty minute craters and white spots, also probably volcanic vents,
and a very curious and interesting series of light streaks, mostly
traversing the formation from E. to W. A little E. of the centre is a
dusky oval area about 6 miles across, and S.W. of this is another, much
smaller. Under some conditions of illumination the two principal light
markings may be traced over the W. wall, and for some distance on the
plain beyond.
On the southern side of Archimedes is a very rugged mountain region,
extending for more than 100 miles towards the south: on the W. of this
originates a remarkable rill-system, best seen under evening
illumination. The two principal clefts follow a nearly parallel course up
to the face of the Apennines near Mount Bradley, crossing in their way,
almost at right angles, other clefts which run at no great distance from
the E. foot of this range and ramify among the outlying hills. Archimedes
A is a brilliant little ring-plain on the S.E. of Archimedes. It casts an
extraordinary shadow at sunrise, and has a well-marked crater-row on the
E. of it, and two long narrow valleys, one of which appears to be a
southerly extension of the row.
BEER.--A very bright little crater, with an unnamed formation of about
the same size adjoining it on the N., with which is associated a curious
winding ridge that appears to traverse a gap in its N. wall.
TIMOCHARIS.--A fine ring-plain, 23 miles in diameter (the centre of a
minor ray-system). It stands isolated on the Mare Imbrium (below the
level of which it is depressed some 3000 feet), about midway between
Archimedes and Lambert. Its walls, rising about 7000 feet above the
floor, are conspicuously terraced, and on their W. outer slopes exhibit
some remarkable depressions. There is a distinct break on the N., and a
bright little crater on the N.W., connected with the foot of the _glacis_
by a prominent ridge. On the bright central mountain, Schmidt, in 1842,
detected a crater, which is easily seen under a moderately high light.
Timocharis and the neighbourhood, especially the peculiar shape of the
terminator on the E. of the formation, is well worth examination at
sunrise.
PIAZZI SMYTH.--A conspicuous little ring-plain, 5 or 6 miles in diameter,
depressed about 1500 feet below the Mare Imbrium, with a border rising
about 2000 feet above it. With the curious arrangement of ridges, of
which it is the apparent centre, it is a striking object under a low sun.
KIRCH.--A rather smaller object of the same class on the S.E.
PLATO.--This beautiful walled-plain, 60 miles in diameter, with its
bright border and dark steel-grey floor, has, from the time of Hevelius
to the present, been one of the most familiar objects to lunar observers.
In the rude maps of the seventeenth century it figures as the "Lacus
Niger Major," an appellation which not inaptly describes its appearance
under a high sun, when the sombre tone of its apparently smooth interior
is in striking contrast to that of the isthmus on which the formation
stands. It will repay observation under every phase, and though during
the last thirty years no portion of the moon has been more diligently
scrutinised than the floor; the neighbourhood includes a very great
number of objects of every kind, which, not having received so much
attention, will afford ample employment to the possessor of a good
telescope during many lunations.
The border of Plato, varying in height from 3000 to 4000 feet above the
interior, is crowned by several lofty peaks, the highest (7400 feet)
standing on the N. side of the curious little triangular formation on the
E. wall. Those on the W., three in number, reckoning from N. to S., are
respectively about 5000, 6000, and 7000 feet in altitude above the floor.
The circumvallation being very much broken and intersected by passes,
exhibits many distinct breaches of continuity, especially on the S. There
is a remarkable valley on the S.W., which, cutting through the border at
a wide angle, suddenly turns towards the S.E., and descends the slope of
the _glacis_ in a more attenuated form. Another but shorter valley is
traceable at sunrise on the W. On the N.W., the rampart is visibly
dislocated, and the gap occupied by an intrusive mountain mass. This
dislocation is not confined to the wall, but, under favourable
conditions, may be traced across the floor to the broken S.E. border. It
is probably a true "fault." On the N.E., the inner slope of the wall is
very broad, and affords a fine example of a vast landslip.
The spots and faint light markings on the floor are of a particularly
interesting character. During the years 1869 to 1871 they were
systematically observed and discussed under the auspices of the Lunar
Committee of the British Association. Among the forty or more spots
recorded, six were found to be crater-cones. The remainder--or at least
most of them--are extremely delicate objects, which vary in visibility in
a way that is clearly independent of libration or solar altitude; and,
what is also very suggestive, they are always found closely associated
with the light markings,--standing either upon the surface of these
features or close to their edges. Recent observations of these spots with
a 13 inch telescope by Professor W.H. Pickering, under the exceptionally
good conditions which prevail at Arequipa, Peru, have revived interest in
the subject, for they tend to show that visible changes have taken place
in the aspect of the principal crater-cones and of some of the other
spots since they were so carefully and zealously scrutinised nearly a
quarter of a century ago. The gradual darkening of the floor of Plato as
the sun's altitude increases from 20 deg. till after full moon may be
regarded as an established fact, though no feasible hypothesis has been
advanced to account for it.
On the N.E. of Plato is a large bright crater, A; and, extending in a
line from this towards the E., is a number of smaller rings, the whole
group being well worth examination. On the N. there is a winding cleft,
and some short crossed clefts in the rugged surface just beyond the foot
of the wall, which I have seen with a 4 inch achromatic. The region on
the W., imperfectly shown in the maps, includes much unrecorded detail.
On the Mare Imbrium S. of Plato is a large area enclosed by low ridges,
to which Schroter gave the name "Newton." It suggests the idea that it
represents the ruin of a once imposing enclosure, of which the
conspicuous mountain Pico formed a part.
TIMAEUS.--A very bright ring-plain, 22 miles in diameter, with walls
about 4500 feet in height, on the coast-line of the Mare Frigoris, and
associated with the E. side of the great enclosed plain W.C. Bond.
Schmidt shows a double hill, nearly central, and Neison a crater on the
S.W. wall.
BIRMINGHAM.--A large rhomboidal-shaped enclosure, defined by mountain
chains and traversed by a number of very remarkable parallel ridges. It
is situated nearly due N. of Plato on the N. edge of the Mare Frigoris,
and lies on the S.E. side of W.C. Bond, to which it bears a certain
resemblance. This region is characterised by the parallelism displayed by
many formations, large and small. It is more apparent hereabouts than in
any other part of the moon's visible surface. When favourably placed
under a low morning sun, Birmingham is a striking telescopic object.
FONTINELLE.--A fine ring-plain, 23 miles in diameter, on the N. margin of
the Mare Frigoris, N.N.E. of Plato, with a wall rising on the E., 6000
feet above a bright interior. I find its border indistinct and nebulous,
excepting under very oblique light, though three of the little craters
upon it are bright and prominent. One stands on the S., another on the
N.W., and a third on the E. Schmidt shows only the first of these, and
Neison none of them. Fontinelle has a low central mountain which is
easily distinguished. Fontinelle A, an isolated mountain on the S., is
more than 3000 feet high. On the N. there is a curious mountain group,
also of considerable altitude, and on the W. an irregular depression
surrounded by a dusky area. North of Fontinelle, extending towards
Goldschmidt and the limb, Schroter discovered a very wide irregular
valley which he named "J.J. Cassini." It is really nothing more than a
great plain bounded by ridges. At 9 h. October 15, 1888, when Philolaus
was on the morning terminator, I had a fine view of it, and, as regards
its general shape, found that it agreed very closely with Schroter's
drawing.
EPIGENES.--A remarkable ring-plain, about 26 miles in diameter, abutting
on a mountain ridge running parallel to the E. flank of W.C. Bond. It is
a notable object under a low morning sun. There are several elevations on
the floor.
GOLDSCHMIDT.--A great abnormally-shaped enclosure with lofty walls
between Epigenes and the limb. Neison mentions only two crater-pits
within. I have seen the rimmed crater shown by Schmidt on the W. side and
three or four other objects of a doubtful kind.
ANAXAGORAS.--A brilliant ring-plain of regular form, 32 miles in
diameter, adjoining Goldschmidt on the E. It is a prominent centre of
light streaks, some of which traverse the interior of Goldschmidt. On the
north a peak rises to the height of 10,000 feet. There is a long ridge on
the floor, running from E. to W.
GIOJA.--A ring-plain about 26 miles in diameter, near the north pole.
EAST LONGITUDE 20 deg. TO 40 deg.
REINHOLD.--A prominent ring-plain, 31 miles in diameter, with a lofty
border, rising at a peak on the W. to more than 9000 feet above the
floor. Its shape on the W. is clearly polygonal, the wall consisting of
three rectilineal sections, and on the E. it is made up of two straight
sections connected by a curved section. The inner slope includes a
remarkably distinct and regular terrace, the E. portion of which is well
seen when the interior is about half illuminated by the rising sun. At
this phase also the great extent of the _glacis_ on the S.W., and the
deep wide gullies traversing it on the E. are observed to the best
advantage. The central mountain, though of considerable size, is not
prominent. Close to Reinhold on the N.W. stands a noteworthy little
formation with a low and partially lineal wall, exhibiting a gap on the
north. There is a distinct crater on the S. side of its floor.
GAY-LUSSAC.--A very interesting ring-plain, 15 miles in diameter,
situated in the midst of the Carpathian Highlands N. of Copernicus, with
a smaller but brighter and deeper formation (Gay-Lussac A) on the S.W. of
it, and a conspicuous little crater, not more than 2 or 3 miles in
diameter, between the two. The interior of Gay-Lussac is traversed by two
coarse clefts, lying nearly in a meridional direction. The more easterly
runs from the foot of the S. wall, near the little crater just mentioned,
across the floor to the low N. border, which it apparently cuts through,
and extends for some distance beyond, terminating in a great oval
expansion. The other, which is not shown in the maps, is closely parallel
to it, and can be traced up to the N. border, but not farther. Schmidt
represents the first as a crater-row, which it probably is, as it varies
considerably in width. From the S.E. side of the formation extends a long
cleft, terminating at the end of a prominent spur from the S. side of the
Carpathians. There are also two remarkable rill-like valleys, commencing
on the N. of Gay-Lussac A, which curve round the W. side of Gay-Lussac.
HORTENSIUS.--This brilliant crater, about 10 miles in diameter, is
remarkable for its depth, and as being a ray-centre surrounded by a
nimbus of light. It has a central mountain, and Schmidt shows a minute
crater on the outer slope of the S. wall. The former is a test object.
MILICHIUS.--Is situated on the N.N.E. of Hortensius. It is fully as
bright, but rather smaller. Its floor, apparently devoid of detail, is
considerably depressed below the surrounding surface.
TOBIAS MAYER.--Like Gay-Lussac, a noteworthy ring-plain associated with
the Carpathian Mountains. It is 22 miles in diameter, and has a wall
which rises on the W. to a height of nearly 10,000 feet above the floor;
on the latter there is a conspicuous central mountain, and on the E. side
a crater, and some little hills. Schmidt shows a smaller crater on the W.
side, which I have not seen. Adjoining the formation on the W. is a ring-
plain of about one-fourth its area, which is a bright object. Tobias
Mayer and the neighbouring Carpathians form an especially beautiful
telescopic picture at sunrise.
KUNOWSKY.--An inconspicuous ring-plain, about 11 miles in diameter,
standing in a barren region in the Mare Procellarum, W.S.W. of Encke. The
central mountain is tolerably distinct.
ENCKE.--A regular ring-plain, 20 miles in diameter, with a comparatively
low border, nowhere rising more than 1800 feet above the interior, which
is depressed some 1000 feet below the surrounding Oceanus Procellarum. A
lofty ridge traverses the floor from S. to N., bifurcating before it
reaches the N. wall. There is a bright crater on the W. wall, and a
depression on the opposite wall, neither of which, strange to say, is
shown on the maps. Encke is encircled by ridges, which, when it is on the
morning terminator, combine to make it resemble a large crater surrounded
by a vast mountain ring.
KEPLER.--One of the most brilliant objects in the second quadrant,--a
ring-plain about 22 miles in diameter, with a lofty border; a peak on the
E. attaining an altitude of 10,000 feet above the surface. The wall is
much terraced, especially the outer slope on the W., where a narrow
valley is easily traceable. Though omitted from the maps, there is a
prominent circular depression on the W. border, which forms a distinct
notch thereon at sunrise. On the N., the wall exhibits a conspicuous
gap. There is a central hill on the floor. Immediately E. of Kepler is a
bright plateau, bounded on the N. by a very straight border, with two
small craters on its edge. Both these objects are incomplete on the N.,
as if they had been deformed by a "fault," which has apparently affected
the N. end of Kepler also. Kepler is the centre of one of the most
extended systems of bright streaks on the moon's visible surface.
BESSARION.--A bright little ring-plain, about 6 miles in diameter, in the
Oceanus Procellarum N. of Kepler. There is a smaller and still brighter
companion on the N. (Bessarion E), standing on a light area. Bessarion
has a minute central hill, difficult to detect.
PYTHEAS.--A small rhomboidal-shaped ring-plain, 12 miles in diameter,
standing in an isolated position on the Mare Imbrium between Lambert and
Gay-Lussac. Its bright walls, rising about 2500 feet above the Mare, are
much terraced within, especially on the E. There is a bright little
crater on the N. outer slope, with a short serpentine ridge running up to
it from the region S. of Lambert, and another winding ridge extending
from the S. wall to the E. of two conspicuous craters, standing about
midway between Pytheas and Gay-Lussac. The former bears a great
resemblance to the ridge N. of Madler, and, like this, appears to
traverse the N. border. The interior of Pytheas, which is depressed more
than 2000 feet below the Mare, includes a brilliant central peak.
LAMBERT.--A ring-plain, 17 miles in diameter, presenting many noteworthy
features. The crest of its border stands about 2000 feet above the Mare
Imbrium, and more than double this height above the interior. The wall is
prominently terraced both within and without; the outer slope on the W.
exhibiting at sunrise a nearly continuous valley running round it. When
near the morning terminator, the region on the N. is seen to be traversed
by some very remarkable ridges and markings; one cutting across the N.
wall appears to represent a "fault." On the S. is a large polygonal
enclosure formed by low ridges. On the W., towards Timocharis, is a
brilliant mountain 3000 feet high, a beautiful little object under a low
sun.
LEVERRIER.--The more westerly of a pair of little ring-plains on the N.
side of the Mare Imbrium, and S.W. of the Laplace promontory. It is about
10 miles in diameter, with walls rising some 1500 feet above the Mare,
and more than 6000 feet above the interior, which seems to be without a
central mountain or other features. Schmidt shows the crater on the N.
rim and another on the S.E. slope, both of which are omitted by Neison,
though they are easy objects when Helicon is on the morning terminator.
About 20 miles on the S.E. there is a very bright little crater on a
faint light area.
HELICON.--The companion ring-plain on the E. It is 13 miles in diameter,
and is very similar, though not quite so deep. There is a crater on the
S.E. wall, and, according to Neison, another on the outer slope of the N.
border. Webb records a central crater. If Helicon is observed when on the
morning terminator, it will be seen to be traversed by a curved ridge
which cuts through the walls, and runs up to a bright crater S.E. of
Leverrier. It appears to be a "fault," whose "downthrow," though slight,
is clearly indicated by an area of lower ground on the E. There is a
great number of small craters in the neighbourhood of this formation.
EULER.--The most easterly of the row of great ring-plains, which,
beginning on the W. with Autolycus, and followed by Archimedes,
Timocharis, and Lambert, extends almost in a great circle from the N.W.
to the S.E. side of the Mare Imbrium. It is about 19 miles in diameter,
and is surrounded by terraced walls, which, though of no great height
above the Mare, rise 6000 feet above the floor. There is a distinct
little gap in the S. wall, easily glimpsed when it is close to the
morning terminator, which probably represents a small crater. Euler has a
bright central mountain, and is a centre of white silvery streaks.
BRAYLEY.--A very conspicuous little ring-plain E.S.E. of Euler, with two
smaller but equally brilliant objects of the same class situated
respectively E. and W. of it.
DIOPHANTUS.--Forms with Delisle, its companion on the N., a noteworthy
object. It is about 13 miles in diameter, with a wall, which has a
distinct break in its continuity on the N., rising about 2500 feet above
the Mare. A rill-valley runs from the E. side of the ring towards the W.
face of a triangular-shaped mountain on the E. of a line joining the
formation with Delisle. North are three bright little craters in a line,
the middle one being much the largest. From the most easterly of these
objects a light streak may be traced under a high sun, extending for many
miles to another small crater on the N.W. of Diophantus, and expanding at
a point due N. of the formation into a spindle-shaped marking. At
sunrise, the W. portion of the streak has all the appearance of a cleft,
with a branch about midway running to the S. side of Delisle. Under the
same phase a broad band of shadow extends from the N.E. wall to the
triangular mountain just mentioned, representing a very sudden drop in
the surface--resembling on a small scale the well-known "railroad" E. of
Thebit. Diophantus has no central mountain.
DELISLE.--A larger and more irregularly-shaped object than the last, 16
miles in diameter, with loftier and more massive walls, and an extensive
but ill-defined central hill. There is an evident break in the northern
border. A triangular mountain on the S.E. and a winding ridge running up
to the N. wall are prominent features at sunrise, as are also the
brilliant summits of a group of hills some distance to the E.N.E.
CARLINI.--A small but prominent and deep little crater about 5 miles in
diameter on the Mare Imbrium about midway between Lambert and the Sinus
Iridum. There are many faint light streaks in the vicinity, one of which
extends from Carlini to Bianchini, on the edge of the Sinus,--a distance
of 300 miles. Schmidt shows a central peak.
CAROLINE HERSCHEL.--A bright and very deep ring-plain about 8 miles in
diameter on the Mare Imbrium, some distance E.N.E. of the last. On the
S.E. lies a larger crater, Delisle B, which has a small but obvious
crater on its N. rim, and casts a very prominent shadow at sunrise.
Caroline Herschel stands on a long curved ridge running N.E. from Lambert
towards the region E. of Helicon, and, according to Schmidt, has a
central peak. On the E. is a bright mountain with two peaks; some
distance N. of which is a large ill-defined white spot, with another spot
of a similar kind on the W. of it, nearly due N. of Caroline Herschel.
GRUITHUISEN.--This ring-plain, 10 miles in diameter, is situated on the
Mare Imbrium on the N.E. of Delisle. It is associated with a number of
ridges trending towards the region N. of Aristarchus and Herodotus.
THE LAPLACE PROMONTORY.--A magnificent headland marking the extreme
western extremity of the finest bay on the moon's visible surface, the
Sinus Iridum; above which it towers to a height of 9000 feet or more,
projecting considerably in front of the line of massive cliffs which
define the border of the Sinus, and presenting a long straight face to
the S.E. Near its summit are two large but shallow depressions, the more
easterly having a very bright interior. At a lower level, almost directly
below the last, is a third depression. All three are easy objects under a
low sun. The best view of the promontory and its surroundings is obtained
when the E. side of the bay is on the morning terminator. Its prominent
shadow is traceable for many days after sunrise.
THE HERACLIDES PROMONTORY.--The less lofty but still very imposing
headland at the E. end of the Sinus Iridum, rising more than 4000 feet
above it. It consists of a number of distinct mountains, forming a
triangular-shaped group running out to a point at the S.W. extremity of
the bay, and projecting considerably beyond the shore-line. There is a
considerable crater on the E. side of the headland, not visible till a
late stage of sunrise. It is among the mountains composing this
promontory that some ingenuity and imagination have been expended in
endeavouring to trace the lineaments of a female face, termed the "Moon-
maiden."
BIANCHINI.--A fine ring-plain, about 18 miles in diameter, on the N.E.
side of the Sinus Iridum, surrounded by the lofty mountains defining the
border of the bay. Its walls, which are prominently terraced within, rise
about 7000 feet on the E., and about 8000 feet on the W. above the floor,
which includes a prominent ridge and a conspicuous central mountain.
There is a distinct crater on the S. wall, not shown in the maps. Between
this side of the formation and the bay is a number of hills running
parallel to the shore-line: these, with the intervening valleys, will
repay examination at sunrise.
MAUPERTUIS.--A great mountain enclosure of irregular shape, about 20
miles in diameter, in the midst of the Sinus Iridum highlands, N. of
Laplace. The walls are much broken by passes, and the interior includes
many hills and ridges.
CONDAMINE.--A rhomboidal-shaped ring-plain, about 23 miles in diameter,
N. of Maupertuis, with lofty walls, especially on the E., where they rise
some 4000 feet above the interior. There are three large depressions on
the outer N.W. slope, and at least three minute craters on the crest of
the wall just above. Though neither Neison nor Schmidt draw any detail
thereon, there is a prominent ridge on the N. side of the floor, and a
low circular hill on the S. On the S.E. four long ridges or spurs radiate
from the wall, and on the N.E. are three remarkable square-shaped
enclosures. On the edge of the Mare Frigoris, N.W. of Condamine, are many
little craters with bright rims and a distinct short cleft, running
parallel to the coast-line. The winding valleys in the region bordering
the Sinus Iridum, and other curious details, render this portion of the
moon's surface almost unique.
BOUGUER.--A bright regular little ring-plain, about 8 miles in diameter,
N. of Bianchini.
J.F.W. HERSCHEL.--A vast enclosed plain, about 90 miles across, bounded
on the W. by a mountain range, which here defines the E. side of the Mare
Frigoris, on the S. by massive mountains, and on the other sides by a
lofty but much broken wall, intersected by many passes. Within is a large
ring-plain, nearly central, and a large number of little craters and
crater-pits. The floor is traversed longitudinally by many low ridges,
lying very close together, which at sunrise resemble fine grooves or
scratches of irregular width and depth.
HORREBOW.--A ring-plain of remarkable shape, resembling the analemma
figure, standing at the S. end of the mountain range bounding J.F.W.
Herschel on the W. Schmidt shows a crater on the W. wall, near the
constriction on this side, and a second at the foot of the slope of the
E. wall.
PHILOLAUS.--A ring-plain 46 miles in diameter, on the N.E. of Fontinelle.
Its bright walls rise on the W. to a height of nearly 12,000 feet above
the floor (on which there is a conspicuous central mountain), and exhibit
many prominent terraces. Philolaus is partially encircled, at no great
distance, by a curved ridge, on which will be found a number of small
craters.
ANAXIMINES.--A much foreshortened ring-plain, about 66 miles in diameter,
on the E. of Philolaus. One peak on the E. is nearly 8000 feet in height.
Schmidt shows four craters on the W. side of the floor, and a fifth on
the S.E. side. There is a bright streak in the interior, which extends
southwards for some distance across the Mare Frigoris.
EAST LONGITUDE 40 deg. TO 60 deg.
REINER.--A regular ring-plain, 21 miles in diameter, in the Mare
Procellarum, S.S.E. of Marius, with a very lofty border terraced without
and within, and a minute but conspicuous mountain standing at the N. end
of a ridge which traverses the uniformly dark floor in a meridional
direction. A long ridge extends some way towards the S. from the foot of
the S. wall, and at some distance in the same direction lie six ill-
defined white spots of doubtful nature. On the E.N.E. there is a large
white marking, resembling a "Jew's harp" in shape, and farther on,
towards the E., a number of very remarkable ridges. On the W. will be
found many bright little craterlets. A ray from Kepler extends almost up
to the W. wall of Reiner.
MARIUS.--A very noteworthy ring-plain, 27 miles in diameter, in the
Oceanus Procellarum, E.N.E. of Kepler, with a bright border rising about
4000 feet above the interior, which is of an uneven tone. The rampart
exhibits some breaks, especially on the S. The outer slope on the W. is
traversed by a fine deep valley, distinctly marked when the opposite side
is on the morning terminator. It originates on the S.W. at a prominent
crater situated a little below the crest of the wall, and, following its
curvature, runs out on to the plain near a large mountain just beyond the
foot of the N. border. In addition to the crater just mentioned, there
are two smaller ones below the summit of the S. wall, and a small
circular depression on the S.E. wall. Mr. W.H. Maw, F.R.A.S., has seen,
with a 6 inch Cooke refractor, a bright marking at the N. extremity of
the ring, which, when examined with a Dawes' eyepiece, resembled an
imperfect crater. The floor includes at least four objects--(1) A crater
on the N.W., standing on a circular light area; (2) a white spot a little
S. of the centre; (3) a smaller white spot S.E. of this; (4) another,
near the inner foot of the S.W. wall. Marius is an imposing object under
oblique illumination, mainly because of the number of ridges by which it
is surrounded. I have frequently remarked at sunrise that the surface on
the W., and especially the outer slope of the rampart, is of a decided
brown or sepia tint, similar to that which has already been noticed with
respect to Geminus and its vicinity, viewed under like conditions.
Schmidt in 1862 discovered a long serpentine cleft some distance N. of
Marius, which has not been seen since.
ARISTARCHUS.--The brightest object on the moon, forming with Herodotus (a
companion ring-plain on the E.), and its remarkable surroundings, one of
the most striking objects which the telescope has revealed on the visible
surface, and one requiring much patient observation before its manifold
details can be fully noted and duly appreciated. Its border rises 2000
feet above the outer surface on the W., but towers to more than double
this height above the glistening floor. No lunar object of its moderate
dimensions (it is only about 29 miles in diameter) has such conspicuously
terraced walls, or a greater number of spurs and buttresses; which are
especially prominent on the S. A valley runs round the outer slope of the
W. wall, very similar to that found in a similar position round Marius.
There is also a distinct valley on the brilliant inner slope of the E.
wall, below its crest. It originates at a bright little crater, and is
traceable round the greater portion of the declivity. Under a moderately
high sun, an oval area, nearly as large and fully as brilliant as the
central mountain, is seen on this inner slope. It is bordered on either
side by bands of a duskier hue, which probably represent shallow
transverse valleys. From its dazzling brilliancy it is very difficult to
observe the interior satisfactorily. In addition, however, to the central
mountain, there is a crater on the N.W. side of the floor. On the S. side
of Aristarchus is a large dusky ring some 10 miles in diameter, connected
by ridges with the spurs from the wall, and on the S.E., close to the
foot of the slope, is another smaller ring of a like kind.
HERODOTUS.--This far less brilliant but equally interesting object is
about 23 miles in diameter, and is not so regular in shape as
Aristarchus. Its W. wall rises at one point more than 4000 feet above the
very dusky floor. Except on the S.W. and N.E., the border is devoid of
detail. On the S.W. three little notches may be detected on its summit,
which probably represent small craters, while on the opposite side, on
the inner slope, a little below the crest, is a large crater, easily
seen. Both the E. and W. sections of the wall are prolonged towards the
S. far beyond the limits of the formation. These rocky masses, with an
intermediate wall, are very conspicuous under oblique illumination, that
on the S.W. being especially brilliant. On the N. there is a gap through
which the well-known serpentine cleft passes on to the floor. Between the
N.W. side of Herodotus and Aristarchus is a large plateau, seen to the
best advantage when the morning terminator lies a little distance E. of
the former. It is traversed by a T-shaped cleft which communicates with
the great serpentine cleft and extends towards the S. end of Aristarchus,
till it meets a second cleft (forming the upper part of the T) running
from the S.E. side of this formation along the W. side of Herodotus. The
great serpentine cleft, discovered by Schroter, October 7, 1787, is in
many respects the most interesting object of its class. It commences at
the N. end of a short wide valley, traversing mountains some distance
N.E. of Herodotus, as a comparatively delicate cleft. After following a
somewhat irregular course towards the N.W. for about 50 miles, and
becoming gradually wider and deeper, it makes a sudden turn and runs for
about 10 miles in a S.W. direction. It then changes its course as
abruptly to the N.W. again for 3 or 4 miles, once more turns to the S.W.,
and, as a much coarser chasm, maintains this direction for about 20
miles, till it reaches the S.E. edge of a great mountain plateau N. of
Aristarchus, when it swerves slightly towards the S., becoming wider and
wider, up to a place a few miles N. of Herodotus, where it expands into a
broad valley; and then, somewhat suddenly contracting in width, and
becoming less coarse, enters the ring-plain through a gap in the N. wall,
as before mentioned. I always find that portion of the valley in the
neighbourhood of Herodotus more or less indistinct, though it is broad
and deep. This part of it, unless it is observed at a late stage of
sunrise, is obscured by the shadow of the mountains on the border of the
plateau. Gruithuisen suspected a cleft crossing the region embraced by
the serpentine valley, forming a connection between its coarse southern
extremity and the long straight section. This has been often searched
for, but never found. It may exist, nevertheless, for in many instances
Gruithuisen's discoveries, though for a long time discredited, have been
confirmed. The mountain plateau N. of Aristarchus deserves careful
scrutiny, as it abounds in detail and includes many short clefts.
HARBINGER, MOUNTAINS.--A remarkable group of moderate height, mostly
extending from the N.W. towards Aristarchus. They include a large
incomplete walled-plain about 30 miles in diameter, defined on the W. by
a lofty border, forming part of a mountain chain, and open to the south.
This curious formation has many depressions in connection with its N.W.
edge. On the N. of it there is a crater-row and a very peculiar zig-zag
cleft. The region should be observed when the E. longitude of the morning
terminator is about 45 deg.
SCHIAPARELLI.--A conspicuous formation, about 16 miles in diameter,
between Herodotus and the N.E. limb, with a border rising nearly 2000
feet above the Mare, and about 1000 more above the floor, on which
Schmidt shows a central hill.
WOLLASTON.--A small bright crater on the Mare N. of the Harbinger
Mountains, surpassed in interest by a remarkable formation a few miles S.
of it, Wollaston B, an object of about the same size, but which is
associated with a much larger enclosure, resembling a walled-plain, lying
on the N. side of it. This formation has a lofty border on the W.,
surmounted by two small craters. The wall is lower on the E. and exhibits
a gap. There is a central hill, only visible under a low sun. About
midway between Wollaston and this enclosure stands a small isolated
triangular mountain. From a hill on the E. runs a rill valley to the more
westerly of a pair of craters, connected by a ridge, on the S.E. of
Wollaston B.
MAIRAN.--A bright ring-plain of irregular shape, 25 miles in diameter, on
the E. of the Heraclides promontory. The border, especially on the E.,
varies considerably in altitude, as is evident from its shadow at
sunrise; at one peak on the W. it is said to attain a height of more than
15,000 feet above the interior. There is a very minute crater on the
crest of the S. wall, down the inner slope of which runs a rill-like
valley. About halfway down the inner face of the E. wall are two other
small craters, connected together by a winding valley. These features may
be seen under morning illumination, when about one-fourth of the floor is
in sunlight. Schroter is the only selenographer who gives Mairan a
central mountain. In this he is right. I have seen without difficulty on
several occasions a low hill near the centre. The formation is surrounded
by a number of conspicuous craters and crater-pits. On the N. there is a
short rill-like valley, and another, much coarser, on the S.
SHARP.--A ring-plain somewhat smaller than the last, on the E. of the
Sinus Iridum, from the coast-line of which it is separated by lofty
mountains. There is a distinct crater at the foot of its N.E. wall, and a
bright central mountain on the floor. On the N. is a prominent enclosure,
nearly as large as Sharp itself; and on the N.E. a brilliant little ring-
plain, A, about 8 miles in diameter, connected with Sharp, as Madler
shows, by a wide valley.
LOUVILLE.--A triangular-shaped formation on the E. of a line joining
Mairan and Sharp. It is hemmed in by mountains, one of which towers 5000
feet above its dusky floor.
FOUCAULT.--A bright deep ring-plain, about 10 miles in diameter, lying E.
of the mountains fringing the Sinus Iridum, between Bianchini and
Harpalus. A very lofty peak rises near its N. border, and, according to
Neison, it has a distinct central mountain, though neither Madler or
Schmidt show any detail within.
HARPALUS.--A conspicuous ring-plain, about 14 miles in diameter, on the
N.E. of the last, with a floor sinking 13,000 feet below the surrounding
surface. As the cubic contents of the border and _glacis_ are quite
inadequate to account for it, we may ask, what has become of the material
which presumably once filled this vast depression? Harpalus has a bright
central mountain.
SOUTH.--On the W. and S., the boundaries of this extensive enclosure are
merely indicated by ridges, which nowhere attain the dignity of a wall.
On the N., the edge of a tableland intersected by a number of valleys
define its limits, and on the E. a border forming also the W. side of
Babbage. The interior is traversed by a number of longitudinal hills, and
includes two bright little heights, drawn by Schmidt as craters.
BABBAGE.--A still larger enclosed area, adjoining South on the E., and
containing a considerable ring-plain near its W. border. It is a fine
telescopic object at sunrise, the interior being crossed by a number of
transverse markings representing ridges. These are very similar in
character (but much coarser) to those found on the floor of J.F.W.
Herschel. The curious detail on the E. wall is also worth examination at
this phase.
ROBINSON.--A bright and very deep little ring-plain, about 12 miles in
diameter, on a plateau N. of South. Schmidt shows a crater on the W.
border, and two others at the foot of the N. and E. borders respectively.
ANAXIMANDER.--A fine but much foreshortened ring-plain, 39 miles in
diameter, abutting on the E. side of J.F.W. Herschel. It has a large
crater on its W. border, which is common to the two formations, and a
very prominent crater, both on the S. and N. The barrier on the S.W.
rises to a height of nearly 10,000 feet. Schmidt shows a crater and other
details on the floor.
EAST LONGITUDE 60 deg. TO 90 deg.
LOHRMANN.--This ring-plain, with Hevel and Cavalerius on the N. of it, is
a member of a linear group, which, but for its propinquity to the limb,
would be one of the most imposing on the moon's surface. Lohrmann, about
28 miles in diameter, is surrounded by a bright wall, which, to all
appearance, is devoid of detail. Two prominent ridges, with a fine
intervening valley, connect it with the N. end of Grimaldi. It has a
large but not conspicuous central mountain. On the rugged surface,
between the ring-plain and the E. edge of the Oceanus Procellarum, lies a
very interesting group of crossed clefts, some of which run from N.E. to
S.W., and others from N.W. to S.E. Three of the latter proceed from
different points in a coarse valley extending from W. to E., and cross
the ridges just mentioned. They follow a parallel course, and terminate
on the S. side of a crater-row, consisting of three bright craters
ranging in a line parallel to the coarse valley. On the N. side of these
objects, and tangential to them, is another cleft, which traverses the W.
and E. walls of Lohrmann, and, crossing the region between it and
Riccioli, terminates apparently at the W. wall of the latter formation.
No map shows this cleft, though it is obvious enough; and, when the E.
wall of Hevel is on the morning terminator, the notches made by it in the
border of Lohrmann are easily detected. Capt. Noble, F.R.A.S., aptly
compares two of the crossed clefts to a pair of scissors, the craters at
which they terminate representing the oval handles. On the grey surface
of the Mare W. of Lohrmann is the bright crater Lohrmann A, from which,
running N., proceeds a rill-like valley ending at a large white spot,
which has a glistening lustre under a high light.
HEVEL.--A great walled-plain, 71 miles in diameter, adjoining Lohrmann on
the N., with a broad western rampart, rising at one peak to a height
above the interior of nearly 6000 feet, and presenting a steep bright
face to the Oceanus Procellarum. There are three prominent craters near
its crest, and one or two breaks in its continuity. It is not so lofty
and is more broken on the E., where three conspicuous craters stand on
its inner slope. The floor is slightly convex, and includes a triangular
central mountain, on which there is a small crater. The S. half of the
interior is crossed by four clefts: (l) running from a little crater N.
of the central mountain, on the W. side of it, to a hill at the foot of
the S.W. wall; (2) originating near the most southerly of the three
craters on the inner slope of the E. wall, and crossing 1, terminates at
the foot of the W. wall; (3) has the same origin as 2, crosses 1, and,
passing over a craterlet W. of the central mountain, also runs up to the
W. wall at a point considerably N. of that where 2 joins the latter; (4)
runs from the craterlet just mentioned to the W. end of 2.
CAVALERIUS.--The most northerly member of the linear chain, a ring-plain,
41 miles in diameter, with terraced walls rising about 10,000 feet above
the floor. Within there is a long central mountain with three peaks.
Under a high light the region on the W. is seen to be crossed by broad
light streaks.
OLBERS.--A large ring-plain, 41 miles in diameter, near the limb, N.E. of
Cavalerius. Though a very distinct formation, it is difficult to see its
details except under favourable conditions of libration. It has a large
crater on its W. wall, a smaller one on the E., and a third on the N. The
floor includes a central mountain, and, according to Schmidt, four
craters. He also shows a crater-rill on the W. wall, N. of the large
crater thereon. Olbers is the origin of a fine system of light rays.
GALILEO.--A ring-plain, about 9 miles in diameter, N.E. of Reiner,
associated with ridges, some of which extend to the "Jew's Harp" marking
referred to under this formation.
CARDANUS.--A fine regular ring-plain, about 32 miles in diameter, near
the limb N. of Olbers. Its bright walls, rising about 4000 feet above the
light grey floor, are clearly terraced, and exhibit, especially on the
S.E., several spurs and buttresses. There is a fine valley on the outer
W. slope, a large bright crater on the Mare just beyond its foot, and a
conspicuous mountain in the same position farther north. I have not
succeeded in seeing the faint central hill nor the crater N. of it shown
by Schmidt, but there is a brilliant white circular spot on the floor at
the inner foot of the N.E. wall which he does not show.
KRAFFT.--A very similar object on the N., of about the same dimensions;
with a central peak, and a large crater on the dark floor abutting on the
S.W. wall, and another of about half the size on the outer side of the W.
border. From this crater a very remarkable cleft runs to the N. wall of
Cardanus: it is bordered on either side by a bright bank, and cuts
through the N.W. border of the latter formation. It is best seen when the
E. wall of Cardanus is on the morning terminator.
VASCO DE GAMA.--A bright enclosure, 51 miles in diameter, with a small
central mountain. It is associated on the N. with a number of enclosed
areas of a similar class, all too near the limb to be well seen.
SELEUCUS.--A considerable ring-plain, 32 miles in diameter, with lofty
terraced walls, rising 10,000 feet above a dark floor which includes an
inconspicuous central hill. This formation stands on a ridge extending
from near Briggs to the W. side of Cardanus.
OTTO STRUVE.--An enormous enclosure, bounded on the E. by the Hercynian
Mountains, and on the W. by a mountain chain of considerable altitude,
surmounted by three or more bright little rings. On the W. side of the
uneven-toned interior, which, according to Madler, includes an area of
more than 26,000 square miles, stand four craters, several little hills,
and light spots. On the W. is the much more regular and almost as large
formation, Otto Struve A, the W. border of Otto Struve forming its E.
wall. This enclosure is bounded elsewhere by a very low, broken, and
attenuated barrier. At sunrise the E. and W. walls, with the mountain
mass at the N. end, which they join, resemble a pair of partially-opened
calipers. There is one conspicuous little crater on the W. side of the
floor; and, at or near full moon, four or five white spots, nearly
central, are prominently visible.
BRIGGS.--This bright regular ring-plain, 33 miles in diameter, is
situated a short distance N. of Otto Struve A. A long ridge traverses the
interior from N. to S. On the E. is another large enclosure,
communicating with Otto Struve on the S., and really forming a N.
extension of this formation. It has a large and very deep crater, 12
miles in diameter, on its W. border.
LICHTENBERG.--A conspicuous little ring-plain, about 12 miles in
diameter, in an isolated position on the Mare, some distance N. of
Briggs. It was here that Madler records having occasionally noticed a
pale reddish tint, which, though often searched for, has not been
subsequently seen.
ULUGH BEIGH.--A good-sized ring-plain, E. of the last, with a bright
border and central mountain. Too near the limb for observation.
LAVOISIER.--A small bright walled-plain N. of Ulugh Beigh. It has a
somewhat dark interior. West of it is Lavoisier A, a ring-plain about 14
miles in diameter. Both are too near the limb for useful observation.
GERARD.--A large enclosure close to the limb, still farther N.,
containing a long ridge and a crater.
HARDING.--A small ring-plain W. of Gerard, remarkable for the peculiar
form of its shadow at sunrise, and for the ridges in its vicinity.
REPSOLD.--The largest of a group of walled enclosures, close to the limb,
on the E. side of the Sinus Roris.
XENOPHANES.--But for its position, this deep walled-plain, 185 miles in
diameter, would be a fine telescopic object, with its lofty walls, large
central mountain, and other details.
OENOPIDES.--A large and tolerably regular walled-plain, 43 miles in
diameter, on the W. of the last. The depressions on the W. wall are worth
examination at sunrise. There is apparently no detail whatever on the
floor.
CLEOSTRATUS.--A small ring-plain, N. of Xenophanes, surrounded by a
number of similar objects, all too near the limb for observation.
PYTHAGORAS.--A noble walled-plain, 95 miles in diameter, which no one who
observes it fails to lament is not nearer the centre of the disc, as it
would then undoubtedly rank among the most imposing objects of its class.
Even under all the disadvantages of position, it is by far the most
striking formation in the neighbourhood. Its rampart rises, at one point
on the N., to a height of nearly 17,000 feet above the floor, on which
stands a magnificent central mountain, familiar to most observers.