EAST LONGITUDE 0 deg. TO 20 deg.
MOSTING.--A very deep ring-plain, 15 miles in diameter, near the moon's
equator, and about 6 deg. E. of the first meridian. There is a crater on
the N. side of its otherwise unbroken bright border, an inconspicuous
central mountain, and, according to Neison, a dark spot on the S. side of
the floor. At some distance on the S.S.W., stands the bright crater,
Mosting A, one of the most brilliant objects on the moon's visible
surface.
REAUMUR.--A large pentagonal enclosure, about 30 miles in diameter, with
a greatly broken border, exhibiting many wide gaps, situated on the E.
side of the Sinus Medii, N.W. of Herschel. The walls are loftiest on the
S. and S.W., where several small craters are associated with them. A
ridge connects the formation with the great deep crater Reaumur A, and a
second large enclosure lying on the W. side of the well-known valley W.
of Herschel. At the end of a spur on the S. side of the great crater
originates a cleft, which I have often traced to the N.W. wall of
Ptolemaeus, and across the N. side of the floor of this formation to a
crater on the N.E. quarter of it, Ptolemaeus _d_. There is a short cleft
on the W. side of the floor of Reaumur, running from N. to S.
HERSCHEL.--A typical ring-plain, situated just outside the N. border of
Ptolemaeus, with a lofty wall rising nearly 10,000 feet above a somewhat
dusky floor, which includes a prominent central mountain. Its bright
border is clearly terraced both within and without, the terraces on the
inner slope of the W. wall being beautifully distinct even under a high
light, and on the outer slope are some curious irregular depressions. On
the S.S.E. is a large oblong deep crater, close to the rocky margin of
Ptolemaeus, and a little beyond the foot of the wall on the N.W. is a
smaller and more regular rimmed depression, _b_, standing near the E.
border of the great valley, more than 80 miles long, and in places fully
10 miles wide, which runs from S.S.W. to N.N.E. on the W. side of
Herschel, and bears a close resemblance to the well-known Ukert Valley.
Herschel _d_ is a large but shallow ring-plain on the E. of Herschel,
with a brilliant but smaller crater on the W. of it.
North of Herschel, on a plateau concentric with its outline, stands the
large polygonal ring-plain Herschel _a_, a formation of a very
interesting character, with a low broken wall, exhibiting many gaps, and
including some craters of a minute class. The largest of these stands on
the S.W. wall. Mr. W.H. Maw has detected some of these objects on the N.
side, both in connection with the border and beyond it.
FLAMMARION.--A large incomplete walled-plain N.E. of Herschel, open
towards the N., with a border rising about 3000 feet above the floor. The
brilliant crater, Mosting A, stands just outside the wall on the E.
PTOLEMAEUS.--Taking its very favourable position into account, this is
undoubtedly the most perfect example of a walled-plain on the moon's
visible superficies. It is the largest and most northerly component of
the fine linear chain of great enclosures, which extend southwards, in a
nearly unbroken line, to Walter. It exhibits a very marked departure from
circularity, the outline of the border approximating in form to a hexagon
with nearly straight sides. It includes an area of about 9000 square
miles, the greatest distance from side to side being about 115 miles. It
is, in fact, about equal in size to the counties of York, Lancashire, and
Westmorland combined; and were it possible for one to stand near the
centre of its vast floor, he might easily suppose that he was stationed
on a boundless plain; for, except towards the west, not a peak, or other
indication of the existence of the massive rampart would be discernible;
and even in this direction he would only see the upper portion of a great
mountain on the wall.
The border is much broken by gaps and intersected by passes, especially
E. and S., where there are several valleys connecting the interior with
that of Alphonsus. The loftiest portion of the wall, which includes many
crateriform depressions, is on the W., where one peak rises to nearly
9000 feet. Another on the N.E. is about 6000 feet above the interior. On
the N.W. is a remarkable crater-row, called, from its discoverer, "Webb's
furrow," running from a point a little N. of a depression on the border
to a larger crateriform depression on the S. of Hipparchus K. Birt terms
it "a very fugitive and delicate lunar feature." As regards the vast
superficies enclosed by this irregular border, it is chiefly remarkable
for the number of large saucer-shaped hollows which are revealed on its
surface under a low sun. They are mostly found on the eastern quarter of
the floor. Some of them appear to have very slight rims, and in two or
three instances small craters may be detected within them. Owing to their
shallowness, they are very evanescent, and can only be glimpsed for an
hour or so about sunrise or sunset. The large bright crater A, about 4
miles in diameter on the N.W. side of the interior, is by far the most
conspicuous object upon it. Adjoining it on the N. is a large ring with a
low border, and N. of this again is another, extending to the wall. Mr.
Maw and Mr. Mee have seen minute craters on the borders of these obscure
formations. In addition to the objects just specified, there is a fairly
conspicuous crater, _d_, on the N.E. quarter of the floor, and a very
large number of others distributed on its surface, which is also
traversed by a network of light streaks, that have recently been
carefully recorded by Mr. A.S. Williams. A cleft, from near Reaumur A,
traverses the N. side of the floor, and runs up to Ptolemaeus _d_.
ALPHONSUS.--A large walled-plain, 83 miles in diameter, with a massive
irregular border abutting on the S.S.E. side of Ptolemaeus, and rising at
one place on the N.W. to a height of 7000 feet above the interior. The
floor presents many features of interest. It includes a bright central
peak, forming part of a longitudinal ridge, on either side of which runs
a winding cleft, originating at a crater-row on the N. side of the
interior. There is a third cleft on the N.W. side, and a fourth near the
foot of the E. wall. There are also three peculiar dark areas within the
circumvallation; two, some distance apart, abutting on the W. wall, and a
third, triangular in shape, at the foot of the E. wall. The last-
mentioned cleft traverses this patch. These dusky spots are easily
recognised in good photographs of the moon.
ALPETRAGIUS.--A fine object, 27 miles in diameter, closely connected with
the S.E. side of Alphonsus. It has peaks on the W. towering 12,000 feet
above the floor, on which there is an immense central mountain, which in
extent, complexity, and altitude surpasses many terrestrial mountain
systems--as, for example, the Snowdonian group. The massive barrier
between Alpetragius and Alphonsus deserves careful scrutiny, and should
be examined under a moderately low morning sun. On the E., towards
Lassell, stands a brilliant light-surrounded crater.
ARZACHEL.--Another magnificent object, associated on the N. with
Alphonsus, about 66 miles in diameter, and encircled by a massive complex
rampart, rising at one point more than 13,000 feet above a depressed
floor. It presents some very suggestive examples of terraces and large
depressions, the latter especially well seen on the S.E. The bright
interior includes a large central mountain with a digitated base on the
S.E., some smaller hills on the S. of it, a deep crater W. of it (with
small craters N. and S.), and, between the crater and the foot of the W.
wall, a very curious winding cleft.
LASSELL.--This ring-plain, some 14 miles in diameter, is irregular both
as regards its outline and the width of its rampart. There is a crater on
the crest of the N.W. wall, just above a notable break in its continuity
through which a ridge from the N.W. passes. There is another crater on
the opposite side. The central mountain is small and difficult to see.
About 20 miles N.E. of Lassell is a remarkable mountain group associated
with a bright crater, and further on in the same direction is a light
oval area, about 10 miles across, with a crater (Alpetragius _d_) on its
S. edge. Madler described this area as a bright crater, 5 miles in
diameter, which now it certainly is not.
LALANDE.--A very deep ring-plain, about 14 miles in diameter, N.E. of
Ptolemaeus, with bright terraced walls, some 6000 feet above the floor,
which contains a low central mountain. On the N. is the long cleft
running, with some interruptions, in a W.N.W. direction towards Reaumur.
DAVY.--A deep irregular ring-plain, 23 miles across, on the Mare E. of
Alphonsus. There is a deep crater with a bright rim on its S.W. wall, and
E. of this a notable gap. There is also a wide opening on the N. The E.
wall is of the linear type. A cleft crosses the interior.
GUERIKE.--The most southerly member of a remarkable group of partially
destroyed walled-plains, standing in an isolated position in the Mare
Nubium. Its border, on the W. and N. especially, is much broken, and
never rises much more than 2000 feet above the Mare, except at one place
on the N., where there is a mountain about 1000 feet higher. The E. wall
is tolerably continuous, but is of a very abnormal shape. On the S. there
is a peculiar LAMBDA-shaped gap (with a bright crater, and another less
prominent on the E. side of it), the narrowest part of which opens into a
long wide winding valley, bounded by low hills, extending to the W. side
of a bright ring-plain, Guerike B, on the S.E. A crater-chain occupies
the centre of this valley. There is much detail within Guerike. A large
deep bright crater stands under the E. border on a mound, which,
gradually narrowing in width, extends to the N. wall; and a rill-like
valley runs from the N. border towards the E. side of the LAMBDA-shaped
gap. In addition to these features, there is a shallow rimmed crater,
about midway between the extremities of the rill-valley, and several
minor elevations on the floor.
On the broken N. flank of Guerike is a number of incomplete little rings,
all open to the N.; and E. of these commences a linear group of lofty
isolated mountain masses extending towards the W. side of Parry, and
prolonged for 30 miles or more towards the north. They are arranged in
parallel rows, and remind one of a Druidical avenue of gigantic monoliths
viewed from above. They terminate on the S. side of a large bright
incomplete ring (with a lofty W. wall), connected with the W. side of
Parry.
PARRY.--A more complete formation than Guerike. It is about 25 miles in
diameter, and is encompassed by a bright border, which, at a point on the
E., is nearly 5000 feet in height. It is intersected on the N. by passes
communicating with the interior of Fra Mauro. There is a crater, nearly
central, on the dusky interior, which, under a low sun, when the shadows
of the serrated crest of the W. wall reach about half-way across the
floor, appears to be the centre of three or four concentric ridges, which
at this phase are traceable on the E. side of it. There is a conspicuous
crater on the E. wall, below which originates a distinct cleft. This
object skirts the inner foot of the E. border, and after traversing the
N. wall, strikes across the wide expanse of Fra Mauro, and is ultimately
lost in the region N. of this formation. Parry A, S. of Parry, is a very
deep brilliant crater with a central hill and surrounded by a glistening
halo. A cleft, originating at a mountain arm connected with the E. side
of Guerike, runs to the S. flank of this object, and is probably
connected with that which skirts the floor of Parry on the E.
BONPLAND.--A ruined walled-plain with a low and much broken wall, which
on the S.W. appears to be an attenuated prolongation of that of Parry. It
is of the linear type, the formation approximating in shape to that of a
pentagon. The floor is crossed from N. to S. by a fine cleft which
originates at a crater beyond the S. wall, and is visible as a light
streak under a high light. Schmidt shows a short cleft on the W. of this.
FRA MAURO.--A large enclosure of irregular shape, at least 50 miles from
side to side, abutting on Parry and Bonpland. In addition to the cleft
which crosses it, the floor is traversed by a great number of ridges, and
includes at least seven craters.
THEBIT.--A fine ring-plain, 32 miles in diameter, on the mountainous W.
margin of the Mare Nubium, N.E. of Purbach. Its irregular rampart is
prominently terraced, and its continuity on the N.E. interrupted by a
large deep crater (Thebit A), at least 9 miles in diameter, which has in
its turn a smaller crater, of about half this size, on its margin, and a
small central mountain within, which was once considered a good optical
test, though it is not a difficult object in a 4 inch achromatic, if it
is looked for at a favourable phase. The border of Thebit rises at one
place on the N.W. to a height of nearly 10,000 feet above the interior,
which includes much detail. The E. wall of Thebit A attains the same
height above its floor, which is depressed more than 5000 feet below the
Mare.
BIRT.--This ring-plain, about 12 miles in diameter, is situated on the
Mare Nubium, some distance due E. of Thebit. It has a brilliant border,
surmounted by peaks rising more than 2000 feet above the Mare, and a very
depressed floor, which does not appear to contain any visible detail. A
bright crater adjoins it on the S.W., the wall of which at the point of
junction is clearly very low, so that under oblique light the two
interiors appear to communicate by a narrow pass or neck filled with
shadow. I have frequently seen a break in the N.W. wall of Birt, which
seems to indicate the presence of a crater. There is a noteworthy cleft
on the E., which can be traced from the foot of the E. wall to the hills
on the N.E. It is a fine telescopic object, and, under some conditions,
the wider portion of it resembles a railway cutting traversing rising
ground, seen from above. It is visible as a white line under a high
light.
THE STRAIGHT WALL.--Sometimes called "the railroad," is a remarkable and
almost unique formation on the W. side of Birt, extending for about 65
miles from N.E. to S.W. in a nearly straight line, terminating on the
south at a very peculiar mountain group, the shape of which has been
compared to a stag's horn, but which perhaps more closely resembles a
sword-handle,--the wall representing the blade. When examined under
suitable conditions, the latter is seen to be slightly curved, the S.
half bending to the west, and the remainder the opposite way. The
formation is not a ridge, but is clearly due to a sudden change in the
level of the surface, and thus has the outward characteristics of a
"fault" Along the upper edge of this gigantic cliff (which, though
measures differ, cannot be anywhere much less than 500 feet high) I have
seen at different times many small craterlets and mounds. Near its N. end
is a large crater, and on the W. is a row of hillocks, running at right
angles to the cliff. No observer should fail to examine the wall under a
setting sun when the nearly perpendicular E. face of the cliff is
brilliantly illuminated.
NICOLLET.--A conspicuous little ring-plain on the E. of Birt, and
somewhat smaller. Between the two is a still smaller crater, from near
which runs a low mountain range, nearly parallel to the straight wall, to
the region S.E. of the Stag's Horn Mountains. Here will be found three
small light-surrounded craters arranged in a triangle, with a somewhat
larger crater in the middle.
PURBACH.--An immense enclosure of irregular shape, approximating to that
of a rhomboid with slightly curved sides. It is fully 60 miles across,
and the walls in places exceed 8000 feet in altitude, and include many
depressions, large and small. On the E. inner slope are some fine
terraces and several craters. The continuity of the circumvallation is
broken on the N. by a great ring-plain, on the floor of which I have seen
a prominent cleft and a crater near the S. side. There is a large bright
crater in the interior of Purbach, S. of the centre, two others on the W.
half of the floor, and a few ridges.
REGIOMONTANUS.--A still more irregular walled-plain, of about the same
area, closely associated with the S. flank of Purbach, having a rampart
of a similar complex type, traversed by passes, longitudinal valleys, and
other depressions. Schmidt alone shows the especially fine example of a
crater-row, which is not a difficult object, in connection with the S.E.
wall. Excepting one crater, nearly central, and some inconspicuous
ridges, I have seen no detail on the floor. Schmidt, however, records
many features.
WALTER.--A great rhomboidal walled-plain, 100 miles in diameter, with a
considerably depressed floor, enclosed by a rampart of a very complex
kind, crowned by numerous peaks, one of which, on the W., rises 10,000
feet above the interior. If the formation is observed when it is close to
the morning terminator, say, when the latter lies from l deg. to 2 deg.
E. of the centre of the floor, it is one of the most striking and
beautiful objects which the lunar observer can scrutinize. The inner
slope of the border which abuts on Regiomontanus, examined at this phase
under a high power, is seen to be pitted with an inconceivable number of
minute craters; and the summit ridge, and the region towards Werner,
scalloped in a very extraordinary way, the engrailing (to use an heraldic
term) being due to the presence of a row of big depressions. The floor at
this phase is sufficiently illuminated to disclose some of its most
noteworthy features. Taking its area to be about 8000 square miles, at
least 1200 square miles of it is occupied by the central mountain group
and its adjuncts, the highest peak rising to a height of nearly 5000 feet
(or nearly 600 feet higher than Ben Nevis), above the interior, and
throwing a fine spire of shadow thereon. In the midst of this central
boss are two deep craters, one being about 10 miles in diameter, and a
number of shallower depressions. In association with the loftiest peak, I
noted at 8 h., March 9, 1889, two brilliant little craters, which
presumably are not far from the summit. Near the E. corner of the floor
there is another large deep crater, and, ranging in a line from the
centre to the S.E. wall, three smaller craters.
LEXELL.--On the E. of Walter extends an immense plain of irregular
outline, which is at least equal to it in area. Though no large formation
is found thereon; many ridges, short crater-rows, and ordinary craters
figure on its rugged superficies; and on its borders stand some very
noteworthy objects, among them, on the S., the walled-plain Lexell, about
32 miles in diameter, which presents many points of interest. Its
irregular wall, rising, at one point on the S.W., to a height of nearly
8000 feet, is on the N.W. almost completely wanting, only very faint
indications of its site being traceable, even under a low morning sun. On
the opposite side it is boldly terraced, and has a large crater on its
summit. The interior, the tone of which is conspicuously darker than that
of the region outside, contains a small central hill, with two craters
connected with it. The low N.W. margin is traversed by a delicate valley,
which, originating on the N. side of the great plain, crosses the W.
quarter of Lexell and terminates apparently on the S.W. side of the
floor.
HELL.--A prominent ring-plain, about 18 miles in diameter, on the E. side
of the great plain. There is a central mountain and many ridges within.
BALL.--A somewhat smaller ring-plain on the S.E. edge of the great plain,
with a lofty terraced border and a central mountain more than 2000 feet
high. There are two large irregular depressions on the W. of the
formation, a crater on the S., and a smaller one on the N. wall.
PITATUS.--This remarkable object, 58 miles in diameter, with Hesiodus,
its companion on the E., situated at the extreme S. end of the Mare
Nubium, afford good examples of a class of formations which exhibit
undoubted signs of partial destruction, from some unknown cause, on that
side of them which faces the Mare. On every side but the N., Pitatus is a
walled plain of an especially massive type, the border on the S.E.
furnishing one of the finest examples of terraces to be found on the
visible surface. On the S.W., two parallel rows of large crateriform
depressions, perhaps the most remarkable of their kind, extend for 60
miles or more to the W. flank of Gauricus. On the N.W., the rampart
includes many curious irregular depressions and craters, and gradually
diminishes in height, till, for a space of about 12 miles on the N.,
there can hardly be said to be any border at all, its site being marked
by some inconsiderable mounds and shallow hollows. There is a small
bright central mountain on the floor, and, S. of it, two larger but lower
elevations. A distinct straight cleft traverses the N.W. side of the
interior very near the wall, to which it forms an apparent chord, and a
second cleft occupies a similar position with respect to the bright N.E.
border. A narrow pass forms a communication with the interior of
Hesiodus.
HESIODUS.--This walled-plain, little more than half the diameter of the
last, has an irregular outline, and for the most part linear walls, which
on the S. are massive and lofty (4000 feet), but on the N. very low, and
broken by gaps. There is a fine deep crater on the S. border, and a small
but distinct crater on the floor, nearly central, the only object thereon
which I have seen, though Schmidt draws a smaller one on the W. of it.
A mountain abutting on the N.E. side of Hesiodus is the W. origin of one
of the longest clefts on the moon. Running in an E.S.E. direction, it
traverses the Mare to a crater near the W. face of the Cichus mountain
arm, reappears on the E. side of this object, and is finally lost amid
the hills on the N. of Capuanus. The W. section of this cleft is coarser
and much more distinct than that lying E. of the mountain arm.
GAURICUS.--A large walled-plain S. of Pitatus, about 40 miles in
diameter. The border is very irregular, and, according to Neison,
consists on the E. of a precipitous cliff more than 9000 feet high. It is
surrounded by a number of large rings on the S., and has several
considerable small depressions on its N. border. There is apparently no
prominent detail on the floor. Schmidt shows some ridges and craterlets.
WURZELBAUER.--Another irregular walled-plain, about 50 miles in diameter,
on the S.E. of Pitatus, with a very complex border, in connection with
which, on the S.W., is a group of fine depressions, and on the S.E. a
large crater. There is much detail on the very uneven floor.
MILLER.--One of a group of three moderately large ring-plains, of which
Nasireddin is a member, near the central meridian in S. latitude 39 deg.
Its massive border rises nearly 11,000 feet above the floor, on which
stands a central peak. Miller is about 36 miles in diameter.
NASIREDDIN.--A somewhat smaller ring-plain on the S. of the last, and of
a very similar type. It contains a central peak and several minor
elevations. Between its N.W. border and the S.W. flank of Miller is a
smaller ring-plain of about half the size of Nasireddin, and on the S.E.
a large enclosure named HUGGINS.
ORONTIUS.--Huggins has encroached on the W. side of this irregular ring-
plain and overlaps it. It is of considerable size. The floor includes
much detail and a prominent crater.
SASSERIDES.--A formation of irregular shape, with very lofty walls,
situated amid the confusion of ring-plains, craters, crater-pits, &c., in
the region N. of Tycho, some of which are fully as deserving of a
distinct name.
HEINSIUS.--A very curious formation on the N.E. of Tycho: a fine
telescopic object under oblique illumination. It has an irregular but
continuous border, except on the S., where two large ring-plains have
encroached upon it, and a third, N. of a line joining their centres,
occupies no inconsiderable portion of the floor. Heinsius is nearly 50
miles across, and the border on the W., is nearly 9000 feet above the
interior, which includes, at least, three small craters. The walls of the
intrusive ring-plains have craters on their summits; the more westerly
has two on the W., and its companion, one on the S.W. The ring-plain on
the floor has a crater on its E. wall. Schmidt shows a small crater
between the ring-plains on the S. border.
SAUSSURE.--A ring-plain W. of Tycho, 28 miles in diameter, with bright
lofty terraced walls and a somewhat dark interior, on which there is a
crater, W. of the centre, and some crater-pits. There are several large
depressions on the S.W. wall. It is surrounded by formations which,
though nearly as prominent as itself, have not, with the exception of
Pictet on the E., and one on the N.W., called Huggins by Schmidt,
received distinctive names. The region W. of Saussure abounds in
craterlets, some of which are of the minutest type. One of the Tycho
streaks is manifestly deflected from its course by this formation, and
another is faintly traceable on the floor.
PICTET.--A walled-plain of irregular shape, about 30 miles across,
between Saussure and Tycho, with a border broken on the S. by a large
conspicuous ring-plain, which is at least 10 miles in diameter, and,
according to Schmidt, has a central mountain. Schmidt draws the S.E.
border of Pictet as broken by ridges extending on to the floor. He also
shows several craters and minor elevations thereon.
TYCHO.--As the centre from which the principal bright ray-system of the
moon radiates, and the most conspicuous object in the southern
hemisphere, this noble ring-plain may justly claim the pre-eminent title
of "the Metropolitan crater." It is more than 54 miles in diameter, and
its massive border, everywhere traversed by terraces and variegated by
depressions within and without, is surmounted by peaks rising both on the
E. and W. to a height of about 17,000 feet above the bright interior, on
which stands a magnificent central mountain at least 5000 feet in
altitude. Were it not somewhat foreshortened, Tycho would be seen to
deviate considerably from what is deemed to be the normal shape. On the
S. and W. especially, the wall approximates to the linear type, no signs
of curvature being apparent where these sections meet. The crest on the
S. and S.E. exhibits many breaks and irregularities; and it is through a
narrow gap on the S. that a rill-like valley, originating at a small
depression near the foot of the S.W. _glacis_, passes, and, descending
the inner slope of the S.E. wall obliquely, terminates near its foot.
There is a distinct crater on the summit ridge on the S.E., and another
below the crest on the outer S.W. slope. On the S. inner slope I have
often remarked a number of bright oval objects, which, for the lack of a
better word, may be termed "mounds" though they represent masses of
material many miles in length and breadth. The outer slope of Tycho,
exhibiting under a high light a grey nimbus encircling the wall,
includes--craters, crater-pits, shallow valleys, spurs and buttresses--in
short, almost every variety of lunar feature is represented. Excepting
the central mountain and a crater on the W. of it, I have not seen any
object on the floor, which, for some unexplained reason, is never very
distinct. Schmidt shows several low ridges on the N.E. side. In a paper
recently published in the _Astronomische Nachrichten_, Professor W.H.
Pickering, describing his observations of the Tycho streaks made at
Arequipa, Peru, with a 13 inch achromatic, asserts that they do not
radiate from the centre of Tycho, but from a multitude of minute craters
on its S.E. or N. rim. (See Introduction.)
MAGINUS.--An immense partially ruined enclosure, at least 100 miles from
side to side, on the S.W. of Tycho, from which it is separated by a
region covered with a confused mass of ring-plains and craters. On almost
every part of its broken border stand large ring-plains, many of which,
if they were isolated, or situated in a less disturbed region, would rank
as objects of importance; but among such a multitude of features they
pass unnoticed. The largest of them occupies no inconsiderable part of
the S.E. wall, and is quite 30 miles in diameter, its own border being
also much broken by depressions, as, indeed, are those of almost all the
six or more large ring-plains which define the N. limits of Maginus. The
loftiest portion of what remains of a true border rises at one place to
more than 14,000 feet. On the floor, which is traversed by some of the
Tycho rays, there is a mountain group associated with a crater, nearly
central, and several large rings on the N. side. Though the formation is
very difficult to detect under a high sun, Madler's dictum that "the full
moon knows no Maginus" is not strictly true.
STREET.--A walled-plain between Tycho and Maginus, about 28 miles in
diameter, with a border of moderate height, broken by depressions on the
N. There are some small craters and ridges within; but the surrounding
region, with its almost endless variety of abnormally shaped formations,
is far more worthy of the observer's attention.
DELUC.--The largest and most prominent member of a curious group of ring-
plains on the S.W. of Maginus. It is about 28 miles in diameter, and is
encircled by a wall some 7000 feet above the interior, which includes a
crater. A large ring with a central mountain encroaches on the N. wall,
and a smaller object of the same class on the S. wall.
CLAVIUS.--There are few lunar observers who have not devoted more or less
attention to this beautiful formation, one of the most striking of
telescopic objects. However familiar we may consider ourselves to be with
its features, there is always something fresh to note and to admire as
often as we examine its apparently inexhaustible details. It is 142 miles
from side to side, and includes an area of at least 16,000 square miles
within its irregular circumvallation, which is only comparatively
slightly elevated above the bright plateau on the W., though it stands at
least 12,000 feet above the depressed floor. At a point on the S.W. a
peak rises nearly 17,000 feet above the interior, while on the E. the
cliffs are almost as lofty. There are two remarkable ring-plains, each
about 25 miles in diameter, associated, one with the N., and the other
with the S. wall, the floors of both abounding in detail. The latter,
however, is the most noteworthy on account of the curious corrugations
visible soon after sunrise on the outer N. slope of its wall, resembling
the ribbed flanks of some of the Java volcanoes. There are five large
craters on the floor of Clavius, following a curve convex to the N., and
diminishing in size from W. to E. The most westerly stands nearly midway
between the two large ring-plains on the walls, the second (about two-
thirds its area) is associated with a complex group of hills and smaller
craters. Both these objects have central mountains. In addition to this
prominent chain, there are innumerable craters of a smaller type on the
floor, but they are more plentiful on the S. half than elsewhere. On the
S.E. wall are three very large depressions. On the broad massive N.E.
border, the bright summit ridge and the many transverse valleys running
down from it to the floor, are especially interesting features. There are
very clear indications of "faulting" on a vast scale where this broad
section of the wall abuts on the N. side of the formation.
CYSATUS.--A regular walled-plain, apparently about 28 miles in diameter,
forming the most northerly member of a chain of formations, of which
Newton, Short, and Moretus, extending towards the S. limb, form a part.
Its border rises nearly 13,000 feet above a floor devoid of prominent
detail.
GRUEMBERGER.--A much larger and more irregular ring-plain, nearly 40
miles from wall to wall, on the E. side of Cysatus. Its W. border rises
nearly 14,000 feet above the interior, which includes an abnormally deep
crater, the bottom of which is 20,000 feet below the crest of the W.
wall, and several small depressions and ridges. The inner E. slope is
finely terraced.
MORETUS.--A magnificent object, 78 miles in diameter, but foreshortened
into a flat ellipse. Its beautifully terraced walls and magnificent
central mountain, nearly 7000 feet high, are very conspicuous under
suitable conditions. The rampart on the E. is more than 15,000 feet above
the floor, while on the opposite side it is about 5000 feet lower.
SHORT.--A fine but foreshortened ring-plain of oblong shape, squeezed in
between Moretus and Newton. It is about 30 miles in diameter, and on the
S.E., where its border and that of Newton are in common, it rises nearly
17,000 feet above the interior, which includes, according to Neison, a
small central hill. Schmidt shows a crater on the N. side of the floor.
NEWTON.--Is situated on the S.E. side of Short, and is the deepest
walled-plain on the visible surface. It is of irregular form and about
143 miles in extreme length. One gigantic peak on the E. rises to nearly
24,000 feet above the floor, the greater part of which is always immersed
in shadow, so that neither the earth or sun can at any time be seen from
it.
MALAPERT.--A ring-plain situated far too near the limb for useful
observation. Between it and Newton is a number of abnormally shaped
enclosures.
CABEUS.--Another object out of the range of satisfactory scrutiny. Madler
considered that it is as deep as Newton. According to Neison, a central
peak and two craters can be seen within under favourable conditions.
Schmidt draws a long row of great depressions on the N. side of it.
EAST LONGITUDE 20 deg. TO 40 deg.
LANDSBERG.--A ring-plain, about 28 miles in diameter, situated in Mare
Nubium, S.E. of Reinhold, which in many respects it resembles. Its
regular massive border is everywhere continuous. Only a solitary crater
breaks the uniformity of its crest, that rises on the W. to nearly 10,000
feet, and on the E. to about 7000 feet above the floor, which is
depressed about 7000 feet below the surrounding surface. The inner slopes
exhibit some fine terraces, and on the broad W. _glacis_ is a curious
winding valley, which runs up the slope from the S.W. side to the crater
just mentioned, then, bending downwards, joins the plain at the foot of
the N. wall. Neither this nor the crater is shown in the maps. The large
compound central peak is apparently the sole object in the interior. At 8
h. 25 m. on January 23, 1888, when observing the progress of sunrise on
this formation with a 8 1/2 inch Calver-reflector charged with different
eyepieces, I noticed, when about three-fourths of the floor was in
shadow, that the illuminated portion of it was of a dark chocolate hue,
strongly contrasting with the grey tone of the surrounding district. This
appearance lasted till the interior was more than half illuminated,
gradually becoming less pronounced as the sun rose higher on the ring. E.
and S.E. of Landsberg is a number of ring-plains and craters well worthy
of careful examination. Five of the largest are surrounded by a
glistening halo, and one (that nearest to the formation) and another (the
largest of the group) have each a minute crater on their N. wall.
EUCLIDES.--One of the most brilliant objects on the moon; a crater 7
miles in diameter, standing on a large bright area in the Mare
Procellarum, E. of the Riphaean Mountains. Its E. rim rises nearly 2000
feet above the bright depressed floor; on the W. there is a bright little
unrecorded crater.
WICHMANN.--This bright crater, about 5 miles in diameter, stands on a
light area in Oceanus Procellarum, N.N.W. of Letronne and nearly due E.
of Euclides. Some distance on the N.E. are the relics of what appears
once to have been a large enclosure, represented now by a few isolated
mountains.
HERIGONIUS.--A ring-plain, about 7 miles in diameter, in the Mare
Procellarum, N.W. of Gassendi. There is a small crater a few miles S.E.
of it, among the bright little mountains which flank this formation.
Herigonius has a small central mountain, which is a good test for
moderate apertures.
GASSENDI.--One of the most beautiful telescopic objects on the moon's
visible surface, and structurally one of the most interesting and
suggestive. It is a walled-plain, 55 miles in diameter, of a distinctly
polygonal type, the N.W. and S.W. sections being practically straight,
while the intermediate W. section exhibits a slightly convex curvature,
or bulging in towards the interior. There is also much angularity about
the E. side, which is evident at an early stage of sunrise. The wall on
the N. is broken through and almost completely wrecked by the great ring-
plain Gassendi A. The bright eastern section of the border is in places
very lofty, rising at one peak, N. of the well-known triangular
depression upon it, to 9000 feet, and at other peaks on the same side
still higher. It is very low on the S., being only about 500 feet above
the surface. The floor, however, on the N. stands 2000 feet above the
Mare Humorum. On the W. there is a peak towering 4000 feet above the
wall, which is here about 5000 feet above the floor, and 8000 feet above
the Mare Nubium. A very notable feature in connection with this formation
is the little bright plain bounding it on the N.W., and separated from it
by merely a narrow strip of wall. This enclosure is flanked on the N.E.
by Gassendi A, and on the S.W. and N.W. by a coarse winding ridge,
running from the W. wall and terminating at a large irregular dusky
depression. Gaudibert has detected a crater near the S.E. edge of this
bright plain, which includes also some oval mounds. The interior of
Gassendi is without question unrivalled for the variety of its details,
and, after Plato, has perhaps received more attention from observers than
any other object. The bright central mountain, or rather mountains, for
it consists of a number of grouped masses crowned by peaks, of which the
loftiest is about 4000 feet, is one of the finest on the moon. It was
carefully studied with a 6 1/4 inch Cooke-achromatic by the late
Professor Phillips, the geologist, who compared it to the dolomitic or
trachytic mountains of the earth. The buttresses and spurs which it
throws out give its base a digitated outline, easily seen under suitable
illumination. There are between 30 and 40 clefts in the interior, the
majority being confined to the S.W. quarter of the floor. Those most
easily seen pertain to the group which radiates from the central mountain
towards the S.W. wall. They are all more or less difficult objects,
requiring exceptionally favourable weather and high powers. A fine
mountain range, the Percy Mountains, is connected with the E. flank of
Gassendi, extending in a S.E. direction towards Mersenius, and defining
the N.E. side of the Mare Humorum.
BULLIALDUS.--A noble object, 38 miles in diameter, forming with its
surroundings by far the most notable formation on the surface of the Mare
Nubium, and one of the most characteristic ring-plains on the moon. It
should be observed about the time when the morning terminator lies on the
W. border of the Mare Humorum, as at this phase the best view is obtained
of the two deep parallel terrace valleys which run round the bright inner
slope of the E. wall, of the crater-row against which they abut on the
S.E., and of the massive W. _glacis_, with its spurs and depressions. The
S. border of Bullialdus has been manifestly modified by the presence of
the great ring-plain A, a deep irregular formation with linear walls,
which is connected with it by a shallow valley. The rampart of Bullialdus
rises about 8000 feet above a concave floor, which sinks some 4000 feet
below the Mare on the E. With the exception of the fine compound central
mountain, 3000 feet high, there are few details in the interior. On the
S., is the fine ring-plain B, connected with the S.E. wall near the
crater-row by a well-marked valley, and nearly due E. of B is another, a
square-shaped enclosure, C, with a very lofty little mountain on the E.
side of it, and a crater on its S. wall. In addition to these features,
there are many ridges and surface inequalities, very prominent under
oblique illumination.
LUBINIEZKY.--A regular enclosure, about 23 miles in diameter, N.E. of
Bullialdus, with a low attenuated border, which is nowhere more than 1000
feet in height. It is tolerably continuous, except on the S., where there
are two or three breaks. Its level dark interior presents no details to
vary its monotony. Close under the N.W. wall is a small crater connected
with it by a ridge, and E. of this a very rugged area, traversed in every
direction by narrow shallow valleys, which are well worth looking at when
close to the morning terminator. A bright spur projects from the N. wall
of Lubiniezky.
KIES.--A somewhat similar formation, S. of Bullialdus, about 25 miles in
diameter, also encircled by a border of insignificant dimensions,
attaining an altitude of 2400 feet at only one point on the S.E., while
elsewhere it is scarcely higher than that of Lubiniezky. It is clearly
polygonal, approximating to the hexagonal type. On the more distinct S.
section a bright spur projects from it. On the N. its continuity is
broken by a distinct little crater. It is traversed by a remarkable white
streak, extending in a S.W. direction from Bullialdus C (where it is very
wide), across the interior, to the more westerly of two craters S.W. of
Mercator. Another streak branches out from it near the centre of the
floor, and runs to the W. wall. The principal streak, so far as the
portion within Kies is concerned, represents a cleft. On the Mare E. of
Kies is a curious circular mound, and farther towards Campanus two
prominent little mountains. On the N.W. is a large obscure ring and a
wide shallow valley bordered by ridges.
AGATHARCHIDES.--A very irregular complex ring-plain, about 28 miles in
diameter, forming part of the N.W. side of the Mare Humorum. It must be
observed under many phases before one can clearly comprehend its
distinctive features. The wall is very deficient on the N., but is
represented in places by bright mountain masses. The formation is flanked
on the E. by a double rampart, which is at one place more than 5000 feet
in height, with a deep intervening valley. The S. wall is traversed by a
number of parallel valleys, all trending towards Hippalus. These are
included in a much wider and longer chasm, which, gradually diminishing
in breadth, extends up to the N. wall of the latter.
HIPPALUS.--A partially ruined walled-plain, about 38 miles in diameter,
on the W. side of the Mare Humorum, S. of Agatharchides. At least one-
third of the border is wanting on the S.E., but under a low sun its site
can be distinguished by a faint marking and the obvious difference in
tone between the dark interior and the lighter-coloured plain. The rest
of the wall is bright and continuous, except at a place on the W., where
what appears to be the segment of a large ring has encroached upon it.
There are two craters in the interior of Hippalus, and a row of parallel
ridges, running obliquely from the S.W. wall up to a cleft which
traverses the floor from N. to S. W. of Hippalus stands a bright crater,
Hippalus A, with an incomplete little ring-plain adjoining it on the
N.W.; and N.E. of it a much larger obscure ring containing two little
hills. The Hippalus rill-system is a very interesting one, and the
greater part of it can, moreover, be easily traced in a good 4 inch
achromatic. It originates in the rugged region E. of Campanus, from which
five nearly parallel curved clefts extend up to the rocky barrier,
connecting the N. side of this formation with the S.W. side of Hippalus.
The most westerly of these furrows is interrupted by a crater on this
wall, but reappears on the N. side of it, and, after making a detour
towards the W. to avoid a little mountain in its path, runs partially
round the E. flank of Hippalus A, and then, continuing its northerly
course, terminates amid the mountains W. of Agatharchides. (A short
parallel cleft runs E. of this from the little mountain to the E. side of
A.) The most easterly member of the system, originating N. of Ramsden,
enters Hippalus at the S. side of the great gap in the border, and, after
traversing the floor at the W. foot of a ridge thereon, also extends
towards the mountains W. of Agatharchides. Between these clefts are three
intermediate furrows, one of which runs N. from the N. side of the
encroaching ring already referred to, on the W. wall of Hippalus.
CAMPANUS.--A ring-plain, 30 miles in diameter, on the rocky barrier,
extending in nearly a straight line from Hippalus to Cichus. Its terraced
walls, which rise on the E. more than 6000 feet above the floor, are
broken on the S. by a narrow valley, and on the E. by a small crater. A
small central mountain is apparently the only object on a very dark
interior.
MERCATOR.--A more irregular ring-plain of about the same area, adjoining
Campanus on the S.W. Its rampart is somewhat lower, and is partially
broken on the N. by two semi-rings, and on the S. by a gap. The E. wall
extends on the S. far beyond the limits of the formation, and terminates
in a brilliant mountain mass 6000 feet in height. There is a bright
crater on the crest of both the E. and W. border. On the plain E. of
Mercator is a remarkable little crater standing on a light area, and,
just under the wall, a dusky pit connected with it by a rill-like
marking. These objects are of a very doubtful nature, and should be
carefully observed. The floor of Mercator is much lighter than that of
Campanus, and appears to be devoid of detail.
CICHUS.--A conspicuous ring-plain, about 20 miles in diameter, with a
prominent deep crater about 6 miles across on its E. rim. It is situated
on a curious boot-shaped plateau, near the S. end of the rocky mountain
barrier associated with the last two formations. Its walls rise about
9000 feet above a sunken floor, on which there is some faint detail, but
apparently nothing deserving the distinction of a central mountain. The
plateau on the N. is cut through by a fine broad valley, which has
obviously interfered with a large crateriform depression on its southern
edge. A cleft runs from a small crater W. of the plateau up to this
valley, and extends beyond to the W. wall of Capuanus. There is also a
delicate cleft crossing the region S. of Cichus to the group of
complicated formations S.W. of Capuanus. As already mentioned, the great
Hesiodus cleft is associated with the Cichus plateau.
CAPUANUS.--A large ring-plain, about 34 miles in diameter, E. of Cichus,
with a border especially remarkable on the E., where it rises more than
8000 feet above the outside country, and includes a large brilliant
shallow crater. It is broken on the N.W. by a small but noteworthy double
crater; and on the S. its continuity is destroyed for many miles by a
number of big circular and sub-circular depressions and prominent deep
valleys, far too numerous and complicated to describe. The level dusky
interior contains only a low mound on the S., but is crossed by some
light streaks running from N. to S.
RAMSDEN.--This ring-plain, 12 miles in diameter, derives its importance
from the remarkable rill-system with which it is so closely associated.
Its border, about 1800 feet on the W. above the outside surface, is
slightly terraced within on the E., where there is an unrecorded bright
crater on the slope. The two principal clefts on the S. originate among
the hills E. of Capuanus. The more easterly begins at a crater on the N.
edge of these objects, and runs N. to the E. side of Ramsden; the other
originates at a larger crater, and proceeds in a N. direction up to a
bright little mountain S.W. of Ramsden; when, swerving to the N.E., it
ends at the W. wall of this formation. This mountain is a centre or node
from which three other more delicate branches radiate. On the N., three
of the shortest clefts pertaining to the system are easily traceable from
neighbouring mountains up to the N. wall, which they apparently partially
cut through. The E. pair have a common origin, but open out as they
approach the border of Ramsden.
VITELLO.--A very peculiar ring-plain, 28 miles in diameter, on the S.
side of the Mare Humorum, remarkable for having another nearly concentric
ring-plain, of considerably less altitude within it, and a large bright
central boss, overlooking the inner wall, 1700 feet in height. The outer
wall is somewhat irregular, and is broken by gaps and valleys on the S.
and N.W. It rises on the E. about 5000 feet above the Mare, but only
about 2000 above the interior, which includes a crater on its N. side,
and some low ridges.
HAINZEL.--This remarkable formation, which is about 55 miles in greatest
length, but is hardly half so broad, derives its abnormal shape from the
partial coalescence of two nearly equal ring-plains, the walls of both
being very lofty,--more than 10,000 feet. It ought to be observed under a
morning sun when the floor is about half illuminated. At this phase the
extension of the broad bright terraced E. border across a portion of the
interior is very apparent, and the true structural character of the
formation clearly revealed. The floor abounds in detail, among which, on
the S., are some large craters and a bright longitudinal ridge. Hainzel
is flanked on the W. and S.W. by a broad plateau, W. of which stand two
ring-plains about 15 miles in diameter, both having prominent central
mountains and bright interiors.
WILHELM I.--A large irregular formation, about 50 miles across, S.E. of
Heinsius, with walls varying very considerably in height, rising more
than 11,000 feet on the E., but only about 7000 feet on the opposite
side. The border is everywhere crowded with depressions, large and small.
Three ring-plains, not less than 6 miles in diameter, stand upon the S.
wall, the most westerly overlapping its shallower neighbour on the E.,
which projects beyond the wall on to the floor. The interior has a very
rugged and uneven surface, upon the N. side of which are two very
distinct craters, and a short crater-row on the W. of them. It is
traversed from W. to E. by three bright streaks from Tycho, two on the N.
being very prominent under a high light.
LONGOMONTANUS.--A much larger walled-plain, S. of the last. It is 90
miles in diameter, with a border much broken by depressions, especially
on the N.E. At one peak on this side it rises to the tremendous altitude
of 13,000 feet above the floor, and at peaks on the W. more than 1000
feet higher. There is a crowd of ring-plains on the N.E. quarter of the
interior, and some hills and craterlets in other parts of it. It is also
crossed by rays from Tycho.
SCHILLER.--A fine lozenge-shaped enclosure, with a continuous but
somewhat irregular border. It is about 112 miles in extreme length, and
rather more than half this in breadth. The loftiest section of the wall
is on the W., where it rises 13,000 feet above a considerably depressed
interior. There is a bright crater on this side and some terraces. On the
broad inner slope of the E. border, the summit ridge of which is
especially well-marked, there is a large shallow depression. The floor
contains scarcely any detail, except some ridges on the N. side and a few
craterlets. The great bright plain E. of Schiller and the region on the
S.E. are especially worthy of scrutiny under a low morning sun.
BAYER.--This object, 29 miles in diameter, with a terraced border rising
on the W. to a height of 8000 feet above the floor, is so closely
associated with Schiller, that it may almost be regarded as forming part
of it. A long lofty mountain arm, apparently connected with the W. wall
of the latter, runs from the E. side of Bayer towards the N.W. There is a
crater on the E. side of the interior.
ROST.--An oblong-shaped ring-plain, 30 miles in diameter, on the S.W. of
Schiller, with moderately high walls, and, according to Neison, a shallow
depression within, nearly central. I have seen a crater shown by Schmidt
on the E. side of the floor. A valley runs from the E. side of Rost to
the S. of Schiller.
WEIGEL.--A not very conspicuous ring-plain on the S. of Schiller, with a
crater on its N.W. rim, and a larger ring adjoining it on the S.E. A
prominent curved mountain arm from the E. wall of Schiller runs towards
the N. side of this formation.
BLANCANUS.--A formation, 50 miles in diameter, on the S.E. side of
Clavius, whose surpassing beauties tend to render the less remarkable
features of this magnificent ring-plain and those of its neighbour
Scheiner less attractive than they otherwise would be. The crest of its
finely terraced wall, which at one peak on the E. rises to 18,000 feet,
is at least 12,000 feet above the interior. Krieger saw twenty craters on
the floor (1894, Sept. 21, 13h.), most of them situated on the S.
quarter.
SCHEINER.--A still larger object, being nearly 70 miles in diameter, with
a prominently terraced wall, fully as lofty as that of Blancanus. There
is a large crater, nearly central, two others on the N.E. side of the
floor, and a fourth at the inner foot of the E. wall. There is also a
shallow ring on the N.E. slope. Schmidt shows, but far too prominently,
two straight ridges crossing each other on the S. side of the central
crater.
CASATUS.--A large walled-plain, about 50 miles in diameter, S.E. of
Blancanus, near the limb, remarkable for having one of the loftiest
ramparts of all known lunar objects; it rises at one peak on the S.W. to
the great height of 22,285 feet above the floor, while there are other
peaks nearly as high on the N. and S. The wall is broken on the E. by a
fine crater. There is also a crater on the N.W. side of the very
depressed floor, together with some craterlets.
KLAPROTH.--Casatus partially overlaps this still larger but less massive
formation on its S.E. flank. The walls of Klaproth are much lower and
very irregular and broken, especially on the W. There are some ridges on
the floor. The neighbouring region is covered with unnamed objects, large
and small.
EAST LONGITUDE 40 deg. TO 60 deg.
FLAMSTEED.--A bright ring-plain, 9 miles in diameter, in a barren region
in the Oceanus Procellarum, N.E. of Wichmann. It has a regular border
(broken at one place on the N. by a gap, which probably represents a
crater), rising to a height of about 1400 feet above the surrounding
plain. A great enclosure, 60 miles in diameter, lies on the N. of
Flamsteed. It is defined by low ridges which exhibit many breaks, though
under a high light the ring is apparently continuous. Within are several
small craters and two considerable hills, nearly central.
HERMANN.--A ring-plain, about 10 miles in diameter, in the Oceanus
Procellarum, W. of Lohrmann. It is associated with a group of long
ridges, running in a meridional direction and roughly parallel to the
coast-line.
LETRONNE.--A magnificent bay or inflexion in the coast-line of the
Oceanus Procellarum, N.N.E. of Gassendi, presenting an opening towards
the N. of nearly 50 miles, and bounded on the S. and S.W. by the lofty
Gassendi highlands. Its border on the W., about 3000 feet high, is
crowned with innumerable small depressions. The interior includes four
bright little mountains, nearly central (three of them forming a
triangle), a bright crater on the W. side, and several minor elevations
and ridges. On the plain N. of the bay, is a large bright crater, from
which a fine curved ridge runs to the central mountains. If Letronne is
observed under oblique illumination, the low mounds and ridges on the
Mare outside impress one with the idea that they represent the remains of
a once complete N. wall.
BILLY.--A ring-plain, 31 miles in diameter, S.E. of Letronne, with a very
dark floor, depressed about 1000 feet below the grey surface on the W.,
and a regular border, rising more than 3000 feet above it. There is a
narrow gap on the S., and indications of a crater on the N.W. rim. Two
small craters stand on the S. half of the interior. The formation is
flanked on the S.W. by highlands.
HANSTEEN.--A somewhat larger ring-plain, with a lower and more
irregular rampart, rising on the W. to nearly 3000 feet above the
floor, which is depressed to about the same extent as that of Billy.
Both the inner and outer slopes are terraced on the E., where the
_glacis_ is traversed by a short, delicate, rill-like valley.
There are some bright curved ridges on the floor. On the W. of Billy
and Hansteen is a wide inlet of the Oceanus Procellarum, bounded by
the Letronne region on the W., and on the S. by lofty highlands. On the
surface, not far from the S.W. border of Hansteen, is a curious
triangular-shaped mountain mass, with a digitated outline on the S., and
including a small bright crater on its area. Between this and the ring-
plain is a large but somewhat obscure depression, N. of which lies a
rill-like object extending from the N. point of the triangular mountain
to the W. wall. At the bottom of a gently sloping valley between Billy
and Hansteen is a delicate marking, which seems to represent a cleft
connecting the two formations.
ZUPUS.--A formation about 12 miles in diameter with a dark floor,
situated in the hilly region N.E. of Mersenius.
FONTANA.--A noteworthy ring-plain, about 20 miles in diameter, E.N.E. of
Zupus, with a bright border, exhibiting a narrow gap on the S. and two
large contiguous craters on the N.W. The faint central mountain stands on
a dusky interior. On the N. is a large peculiar depressed plain with a
gently sloping wall, within which are three short rill-like valleys and a
crater.
MERSENIUS.--With its extensive rill-system and interesting surroundings,
one of the most notable ring-plains in the third quadrant. It is 41 miles
in diameter, and is encircled by a fine rampart, which on the side
fronting the Mare Humorum rises 7000 feet above the floor, which is
distinctly convex, and is depressed 3000 feet below the region on the E.,
though it stands considerably above the level of the Mare. The
prominently terraced border is tolerably regular on the N.W., but on the
S. and S.E. is much broken by craters and depressions, the largest and
most conspicuous interrupting the continuity of its summit-ridge on the
latter side. A fine crater-row traverses the central part of the
interior, nearly axially, and a delicate cleft crosses the N. half of the
floor from the inner foot of the N.E. wall to a crater not far from the
opposite side. I detected another cleft on November 11, 1883, also
crossing the N. side of the floor.
South of Mersenius is the fine ring-plain Mersenius _d_, about 20 miles
in diameter, situated on the border of the Mare; and, extending in a line
from this towards Vieta are two others (_a_, and Cavendish _d_,),
somewhat larger, but otherwise similar; the more easterly being connected
with Cavendish by a mountain arm. One of the principal clefts of the
system (all of which run roughly parallel to the N.E. side of the Mare,
and extend to the Percy Mountains E. of Gassendi) crosses the floor of
_d_, and, I believe, partially cuts into its W. wall. Another, the
coarsest, abuts on a mountain arm connecting _d_ with Mersenius, and,
reappearing on the E. side, runs up to the N.W. wall of the other ring-
plain, _a_, and, again reappearing on the E. of this, strikes across the
rugged ground between _a_ and Cavendish _d_, traversing its floor and
border, as does also another cleft to the N. of it. Cavendish _d_
includes a coarse cleft on its floor, running from N. to S., which I have
frequently glimpsed with a 4 inch achromatic. There are two other
delicate clefts running from the Gassendi region to the S.W. side of
Mersenius, which are in part crater-rills.
CAVENDISH.--A notable ring-plain, 32 miles in diameter, S.E. of
Mersenius, with a prominently terraced border, rising at one point on the
S. to a height of 6000 feet above the interior, on which are a few low
ridges. A large bright ring-plain (_e_), about 12 miles in diameter,
breaks the continuity of the S.E. wall, and adjoining this, but beyond
the limits of the formation, is another smaller ring with a central hill.
There is also a bright crater on the N.W. border. The W. _glacis_ is very
broad, and includes two large shallow depressions. An especially fine
valley runs up to the N. wall, to the W. side of _e_.
VIETA.--One of the finest objects in the third quadrant; a ring-plain 51
miles in diameter, with broad lofty walls, a peak on the west rising to
nearly 11,000 feet, and another N. of it to considerably more than 14,000
feet above the interior. It is bounded by a linear border, approximating
very closely to an hexagonal shape, which is broken by many gaps and
cross-valleys. On the S., the S.W. and S.E. sections of the wall do not
meet, being separated by a wide valley flanked on the W. by a fine
crater, which has broken down the rampart at this place. The N. border is
likewise intersected by valleys and by a crater-row. The inner slopes are
conspicuously terraced. There is a very inconspicuous central mountain
and several large craters on the floor, some of them double. Ten have
been counted on the N. half of the interior. On the S.E. of Vieta are two
fine overlapping ring-plains, with a crater on the wall common to both.
DE VICO.--A conspicuous little ring-plain, about 9 miles in diameter,
with a lofty border, some distance E. of Mersenius.
LEE.--An incomplete walled-plain, about 28 miles in diameter, on the S.
side of the Mare Humorum, E. of Vitello, from which it is separated by
another partial enclosure, with a striking valley, not shown in the
published maps, running round its W. side. If viewed when its E. wall is
on the morning terminator, some isolated relics of the wrecked N.W. wall
of Lee are prominent, in the shape of a number of attenuated bright
elevations separated by gaps. Within are three or four conspicuous hills.
DOPPELMAYER.--Under a high sun this large ring-plain, 40 miles in
diameter, resembles a great bay open to the N.W., without a trace of
detail to break the monotony of the surface on the side facing the Mare
Humorum. When, however, it is viewed under oblique morning illumination,
a low broad ridge is easily traceable, extending across the opening,
indicating the site of a ruined wall. There is an isolated mountain at
the S.W. end of this, which casts a fine spire of shadow across the floor
at sunrise. The interior contains a massive bright central mountain and
several little hills. The crest of the wall on the E. is much broken.
FOURIER.--A large ring-plain, 30 miles in diameter, S.W. of Vieta, with a
border rising at a peak on the W. more than 9000 feet above the floor,
There are two craters on the outer slope of the N.W. wall, a prominent
crater on the S. wall, and (according to Schmidt) a small central crater
on the floor, which I have not seen. In the region between Fourier and
Vieta there are three ring-plains, two (the more westerly) standing side
by side, and on the W., towards the Mare, are two others much larger,
that nearer to Fourier being traversed by one cleft, and the other by two
clefts, crossing near the centre of the floor.
CLAUSIUS.--A small bright ring-plain in an isolated position N.W. of
Schickard, with a crater both on its N. and S. rim, and a faint central
hill.
LACROIX.--A ring-plain 20 miles in diameter, N. of Schickard. It has a
prominent central mountain.
SCHICKARD.--One of the largest wall-surrounded plains on the visible
surface of the moon, extending about 134 miles from N. to S., and about
the same from E. to W., enclosing a nearly level area, abounding in
detail. Its border, to a great extent linear, is very irregular, and much
broken by the interposition of small ring-plains and craters, and on the
N. by cross-valleys. Its general height is about 4000 feet, the loftiest
peak on the W. wall rising to more than 9000 feet above the floor. The
inner slopes of this vast rampart are very complex, especially on the E.,
where many terraces and depressions may be seen under suitable
illumination. There are three large ring-plains in the interior, all of
them S. of the centre; and at least five smaller ones near the inner foot
of the E. wall, which can only be well observed when libration is
favourable. The two more easterly of the large ring-plains are connected
by a cleft, and there are several short clefts and crater-rows associated
with the smaller ring-plains. On the N. side of the area is a number of
minute craters. The floor is diversified by two large dark markings--an
oblong patch on the S.W. side, abutting on the wall, being the more
remarkable; and a dusky area, occupying a great portion of the N. part of
the floor, and extending up to the N. border. This is traversed by a
light streak running from N. to S., which is the site of a row of minute
craters.
LEHMANN.--A ring-plain, about 28 miles in length, on the N. of Schickard,
with which it is connected by a number of cross-valleys.
DREBBEL.--A bright ring-plain, 18 miles in diameter, on the N.W. of
Schickard, with a lofty irregular border (especially on the W.),
exhibiting a well-marked terrace on the E., a distinct gap on the N., and
a small crater on the S.E. rim. On a dusky area between it and Schickard
stand three prominent deep craters.
PHOCYLIDES.--This extraordinary walled plain, with its neighbouring
enclosures, is structurally very remarkable and suggestive. It consists
of a large irregular formation, with a lofty wall, flanked on the N. by a
smaller and still more irregular enclosure (_b_), the floor of which is
1500 feet above that of Phocylides, the line of partition being a high
cliff, probably representing a "fault," whose shadow under a low sun is
very striking. Phocylides is about 80 miles in maximum length, or, if we
reckon the small enclosure _b_ to form a part of it, more than 120 miles.
The loftiest peak, nearly 9000 feet, is on the W. border, near the
partition wall. The continuity of the rampart is broken on the S. by a
large crater. There is a bright ring-plain on the W. side of the floor,
and a few small craters. Phocylides _b_ has only a solitary crater within
it. Phocylides C, abutting on the W. flank of Phocylides, is about 26
miles in diameter. Its somewhat dusky interior is devoid of detail, but
the outer slope of its W. wall is crowded with a number of minute
craters, which, under good conditions, may be utilised as tests of the
defining power of the telescope used. Phocylides A, on the bright S.W.
plain, is a large deep crater with a fine crater-row flanking it on the
W.
WARGENTIN.--A most remarkable member of the Phocylides group, flanking
the S.E. side of Schickard. Unlike the majority of lunar formations, its
floor is raised considerably above the surrounding region, so that it
resembles a shallow oval dish turned upside down. It is 54 miles in
diameter, and, except on the S.W. (where it abuts on Phocylides _b_, and
for some distance is bounded by its wall), it has only a border of very
moderate dimensions. On the N.E. slope of this ghostly rampart I have
seen a distinct little crater, and two much larger depressions on the
N.W. slope. There are some low ridges on the floor, radiating from a
nearly central point, which have been aptly compared to a bird's foot.
SEGNER.--A fine ring-plain, 46 miles in diameter, on the S.E. side of
Schiller, with a linear border on every side except the N. At a peak on
the W., whose shadow is very remarkable, it rises to a height of more
than 8000 feet above the outer surface. There is a crater on the S.W.
wall, another on the N.W. wall, and several depressions on the outer
slope on this side. The central mountain is small but conspicuous. A
large unnamed enclosure extends N. of Segner: it is larger than Schiller,
and is surrounded by a lofty barrier. The bright plain between this and
the latter is worth examination under a low sun.
ZUCHIUS.--Is situated on the S.E. of Segner, which it slightly overlaps.
It is very similar in size and general character, and has a lofty
terraced wall, rising at one place on the W. to nearly 11,000 feet above
the floor. A very fine chain of craters, well seen when the opposite
border is on the morning terminator, runs round the outer W. slope of the
wall. There is a bright crater beyond this on the S.W. Zuchius has a
central peak.
BETTINUS.--Another ring-plain of the same type and size, some distance S.
of the last, with a massive border, terraced within, and rising on the W.
more than 13,000 feet above the floor, on which stands a grand central
mountain, whose brilliant summit is in sunlight a long time before a ray
reaches any part of the deep interior.
KIRCHER.--A ring-plain, about 45 miles in diameter, S. of Bettinus,
remarkable also for its very lofty rampart, which on the S. attains the
tremendous height of nearly 18,000 feet above the floor, which appears to
be devoid of detail.
WILSON.--The most southerly of the chain of five massive ring-plains,
extending in an almost unbroken line from Segner and differing only very
slightly in size. It is about 40 miles in diameter, and has a somewhat
irregular border, both as regards shape and height, rising at one peak on
the S.W. to nearly 14,000 feet above a level interior, which apparently
contains no conspicuous features.
EAST LONGITUDE 60 deg. TO 90 deg.
GRIMALDI.--This ranks among the largest wall-surrounded plains on the
moon, and is perhaps the darkest. It extends 148 miles from N. to S. and
129 miles from E. to W., enclosing an area of some 14,000 square miles,
or nearly double that of the principality of Wales. This vast dusky
surface is bounded on the E. by a tolerably regular border, having an
average height of about 4000 feet, while on the opposite side it is much
broken, and in places considerably loftier, rising at one peak on the
S.W. to an altitude of 9000 feet. About midway, also, this western
rampart attains a great height, as may be seen by any one who observes at
sunrise the magnificent shadow of it, and its many peaks thrown across
the bluish-grey interior. On the S. the wall is broken by a large
irregular depression, on the W. of which is a very curious V-shaped rill
valley. On the N.W. it is comparatively low, and in places discontinuous;
and even to a greater extent than on the S.W., intersected by passes. At
the extreme N. end, a number of wide valleys cut through the wall and
trend towards Lohrmann. There is a considerable ring-plain at the inner
foot of the N.E. wall, but, except this and a few longitudinal ridges,
just visible under a very low sun, there is apparently no other object to
vary the monotony of this great expanse.
DAMOISEAU.--Consists of a complex arrangement of rings, an enclosure 23
miles in diameter, with a somewhat smaller enclosure placed excentrically
within it (the N. side of both abutting on a bright plateau), with two
large depressions intervening between their W. borders. This peculiarity,
almost unique, renders the formation an especially interesting object.
Damoiseau is situated on the W. side of Grimaldi, on the E. coast-line of
the Oceanus Procellarum, from which the S.W. border rises at a gentle
inclination. On the N.W. there is a curious curved inflexion of the Mare,
bounded by a bright cliff, representing probably the E. side of a
destroyed ring, a supposition which is strengthened by the existence of a
faint scar on the surface of the sea, extending in a curve from one
extremity of the bay to the other, and thus indicating the position of
the remainder of the ring. A conspicuous little crater stands at the S.
end of it, and two others some distance to the W. The smaller component
of Damoiseau contains a low central ridge.
RICCIOLI.--An immense enclosure, near the limb, N.E. of Grimaldi, bounded
by a rampart which is very irregular both in form and height, though
nowhere of great altitude, and much broken by narrow gaps. It is
especially low and attenuated on the N., where a number of ridges with
intervening valleys traverse it. On the S. also a wide valley cuts
through it. With the exception of a few low rounded hills and ridges, a
short crater-row under the S.E. wall, and two small craters on the S.W.,
there are no details on the floor, which, however, is otherwise
remarkable for the dusky tone of its surface, especially on the N. This
dark patch occupies the whole of the N.E. side of the interior, and is
bounded on the S. by an irregular outline, extending at one point nearly
to the centre, and on the W. by a curved edge. The W. side is much darker
than the rest. It is, in fact, as dark, if not darker, than any part of
the floor of Grimaldi. Riccioli extends 106 miles from N. to S., and is
nearly as broad. It includes an area of 9000 square miles.
ROCCA.--An irregular formation, 60 miles in length, near the limb S.E. of
Grimaldi, consisting of a depression partially enclosed by mountain arms.
SIRSALIS.--The more westerly of a conspicuous pair of ring-plains about
20 miles in diameter, in the disturbed mountain region some distance S.W.
of Grimaldi. It has lofty bright walls, rising to a great height above a
depressed floor, on which there is a prominent central mountain. The E.
border encroaches considerably on the somewhat larger companion, which
is, however, scarcely a third so deep. One of the longest clefts on the
visible surface runs immediately W. of this formation. Commencing at a
minute crater on the N. of it, it grazes the foot of the W. _glacis_;
then, passing a pair of small overlapping craters (resembling Sirsalis
and its companion in miniature), it runs through a very rugged country to
a ring-plain E. of De Vico (De Vico _a_), which it traverses, and, still
following a southerly course, extends towards Byrgius, in the
neighbourhood of which it is apparently lost at a ridge, though Schmidt
and Gaudibert have traced it still farther in the same direction. It is
at least 300 miles in length, and varies much in width and character,
consisting in places of distinct crater-rows.
CRUGER.--A regular ring-plain E. of Fontana, 30 miles in diameter, with a
dark floor, without detail, and comparatively low bright walls. There is
a smaller but very conspicuous ring-plain (Cruger _a_) on the W. of it,
to which runs a branch of the great Sirsalis cleft.
EICHSTADT.--A ring-plain, 32 miles in diameter, near the E. limb, S. of
Rocca. It is the largest and most southerly of three nearly circular
enclosures, without central mountains or any other details of interest.
On the W. lies a great walled-plain with a very irregular border,
containing several ring-plains and craters, and a crater-rill. Schmidt
has named this formation DARWIN.
BYRGIUS.--A very irregular enclosure, about 40 miles in diameter, between
Cavendish and the E. limb, with a lofty and discontinuous border, rising
at one point on the E. to a height of 7000 feet above the floor. There
are wide openings both in the N. and S. wall, and some ridges within. The
border is broken on the E. by a crater, and on the W. by the well-known
crater Byrgius A, from which a number of bright streaks radiate, mostly
towards the E. One on the W. extends to Cavendish, and another to
Mersenius, traversing the ring-plain Cavendish C. North-east of Byrgius
there is a mountain arm which includes a peak 13,000 feet in height.
PIAZZI.--A walled-plain, about 90 miles in length, some distance S.E. of
Vieta, with a complex broken border, including several depressions on the
N.W., rising to about 7000 feet above a rather dark interior, on which
there is a prominent central mountain.
LAGRANGE.--A larger but similar formation, 100 miles in diameter,
associated with the last on the N.E., with a complex terraced border,
including peaks of 9000 feet, a bright crater on the W., and a ring-plain
on the N.W. The inner slope of the E. wall is a fine object at sunrise,
when libration is favourable. The floor is dark and devoid of detail.
BOUVARD.--A great irregular enclosure, which appears to be still larger
than Lagrange, S.E. of Piazzi, and close to the limb. It is bounded by a
very lofty rampart, rising at a peak on the W. to 10,000 feet. It has a
fine central mountain.
INGHIRAMI.--A very remarkable ring-plain, 60 miles in diameter, E. of
Schickard, with a bright, broad, and nearly continuous border, terraced
within, and intersected on the N.E. by narrow valleys, one of which is
prolonged over the floor and extends to the central mountain. There are
two curious dark spots on the N. side of the interior. Beyond the foot of
the _glacis_ on the S. a distinct cleft runs from a dusky spot to a group
of small craters E. of Wargentin. There is a fine regular ring-plain with
a small central mount W. of Inghirami.
PINGRE.--A ring-plain, about 18 miles in diameter, between Phocylides and
the limb.
HAUSEN.--A ring-plain, close to the limb, N. of Bailly, which, but for
its position, would be a fine object. It is, however, never sufficiently
well placed for observation.
BAILLY.--One of the largest wall-surrounded plains on the moon, almost a
"sea" in miniature, extending 150 miles from N. to S., and fully as much
from W. to E. When caught at a favourable phase, it is, despite its
position, especially worthy of scrutiny. The rampart on the W., of the
linear type, is broken by several bright craters. On the S.W. two
considerable overlapping ring-plains interfere with its continuity. On
the S.E. several very remarkable parallel curved valleys traverse the
border. The E. wall, which at one point attains a height of nearly 15,000
feet, is beautifully terraced. The floor on the eastern side includes
several ring-plains (some of which are of a very abnormal type), many
ridges, and two delicate dark lines, crossing each other near the S. end,
probably representing clefts.
LEGENTIL.--A large walled-plain, close to the limb, S. of Bailly.