HALLEY.—A ring-plain, 21 miles in diameter, on the S.W. border of Hipparchus, with a bright wall, rising at one point on the E. to a height of 7500 feet above the floor, which is depressed about 4000 feet below the surface. Two craterlets on the floor, one discovered by Birt on Rutherfurd's photogram of 1865, and the other by Gaudibert, raised a suspicion of recent lunar activity within this ring. A magnificent valley, shown in part by Schmidt as a crater-row, runs from the S. of Halley to the W. side of Albategnius.

HIND.—A ring-plain, 16 miles in diameter, a few miles W. of Halley, with a peak on its E. wall 10,000 feet above the floor. The border is broken both on the S.E. and N.E. by small craters.

[Horrocks, Halley, and Hind may be regarded as strictly belonging to Hipparchus.]

ALBATEGNIUS.—A magnificent walled-plain, 65 miles in diameter, adjoining Hipparchus on the S., surrounded by a massive complex rampart, prominently terraced, including many depressions, and crossed by several valleys. It is surmounted by very lofty peaks, one of which on the N.E. stands nearly 15,000 feet above the floor. The great ring-plain Albategnius A, 28 miles in diameter, intrudes far within the limits of the formation on the E., and its towering crest rises more than 10,000 feet above its floor, on which there is a small central mountain. The central mountain of Albategnius is more than 4000 feet high, and, with the exception of a few minor elevations, is the only prominent feature in the interior, though there are many small craters. Schmidt counted forty with the Berlin refractor, among them 12 on the E. side, arranged like a string of pearls.

PARROT.—An irregularly-shaped formation, 41 miles in diameter, S. of Albategnius, with a very discontinuous margin, interrupted on every side by gaps and depressions, large and small; the most considerable of which is the regular ring-plain Parrot a, on the E. An especially fine valley, shown by Schmidt to consist in part of large inosculating craters, cuts through the wall on the S.W., and runs on the E. side of Argelander towards Airy. The floor of Parrot is very rugged.

DESCARTES.—This object, about 30 miles in diameter, situated N.W. of Abulfeda, is bounded by ill-defined, broken, and comparatively low walls; interrupted on the S.E. by a fine crater, Descartes A, and on the S.W. by another, smaller. There is also a brilliant crater outside on the N.W. Schmidt shows a crater-row on the floor, which I have seen as a cleft.

DOLLOND.—A bright crater, about 6 miles in diameter, on the N.E. side of Descartes. Between it and the latter there is a rill-valley.

TACITUS.—A bright ring-plain, about 28 miles in diameter, a few miles E. of Catherina, with a lofty wall rising both on the E. and W. to more than 11,000 feet above the floor. Its continuity is broken on the N. by a gap occupied by a depression, and there is a conspicuous crater below the crest on the S.W. The central mountain is connected with the N. wall by a ridge, recalling the same arrangement within Madler. A range of lofty hills, an offshoot of the Altai range, extends from Tacitus towards Fermat.

ALMANON.—This ring-plain, with its companion Abulfeda on the N.E., is a very interesting telescopic object. It is about 36 miles in diameter, and is surrounded by an irregular border of polygonal shape, the greatest altitude of which is about 6000 feet above the floor on the W. It is slightly terraced, and is broken on the S. by a deep crater pertaining to the bright and large formation Tacitus b, the E. border of which casts a fine double-peaked shadow at sunrise. On the N.W. there is another bright crater, the largest of the row, running in a W.S.W. direction, and forming a W. extension of the remarkable crater-chain tangential to the borders of Almanon and Abulfeda. The only objects on the floor are three little hills, in a line, near the centre, a winding ridge on the W. side of it, and two or three other low elevations.

ABULFEDA.—A larger and more massive formation than Almanon, 39 miles in diameter, the E. wall rising about 10,000 feet above the interior, which is depressed more than 3000 feet. It is continuous on the W., but much broken by transverse valleys on the S.E., and by little depressions on the N. On the S.E. originates the very curious bright crater-row which runs in a straight line to the N.W. wall of Almanon, crossing for the first few miles the lofty table-land lying on the S.E. side of the border. With the exception of a low central mountain, the interior of Abulfeda contains no visible detail. The rampart is finely terraced on the E. and W. The E. glacis is very rugged.

ARGELANDER.—This conspicuous ring-plain, about 20 miles in diameter, is, if we except two smaller inosculating rings on the S.W. flank of Albategnius, the most northerly of a remarkable serpentine chain of seven moderately-sized formations, extending for nearly 180 miles from the S.W. of Parrot to the N. side of Blanchinus. Its border is lofty, slightly terraced within, and includes a central peak.

AIRY.—About 22 miles in diameter, connected with Argelander by a depression bounded by linear walls. Its border, double on the S.E., is broken on the S. by a prominent crater, with a smaller companion on the W. of it; and again on the N.E. by another not so conspicuous. It has a central peak. The next link in the chain of ring-plains is Airy c, a very irregular object, somewhat larger, and with, for the most part, linear walls.

DONATI.—A ring-plain on the S. of Airy c, about 22 miles in greatest length. It is very irregular in outline, with a lofty broken border, especially on the N. and S., where there are wide gaps. There is another ring on the S.E.

FAYE.—The direction of the chain swerves considerably towards the E. at this formation, which resembles Donati both in size and in irregularity of outline. The wall, where it is not broken, is slightly terraced. There is a craterlet on the S. rim and a central crater in the interior.

DELAUNAY.—Adjoins Faye on the S.E., and is a larger and more complex object, of irregular form, with very lofty peaks on its border. A prominent ridge of great height traverses the formation from N. to S., abutting on the W. border of Lacaille. Delaunay is the last link in the chain commencing with Argelander.

LACAILLE.—An oblong enclosure situated on the N. side of Blanchinus, and apparently about 30 miles in greatest diameter. The border is to a great extent linear and continuous on the N., but elsewhere abounds in depressions. Two large inosculating ring-plains are associated with the N.E. wall.

BLANCHINUS.—A large walled-plain on the W. of Purbach and abutting on the S. side of Lacaille. It much resembles Purbach in shape, but has lower walls. Schmidt shows a crater on the N. side of the floor, which I have seen, and a number of parallel ridges which have not been noted, probably because they are only visible under very oblique light.

GEBER.—A bright ring-plain, 25 miles in diameter, S. of Almanon, with a regular border, rising to a height on the W. of nearly 9000 feet above the floor. There is a small crater on the crest of the S. wall, and another on the N. A ring-plain about 8 miles in diameter adjoins the formation on the N.E. According to Neison, there is a feeble central hill, which, however, is not shown by Schmidt.

SACROBOSCO.—This is one of those extremely abnormal formations which are almost peculiar to certain regions in the fourth quadrant. It is about 50 miles in greatest diameter, and is enclosed by a rampart of unequal height, rising on the E. to 12,000 feet above the floor, but sinking in places to a very moderate altitude. On the N. its contour is, if possible, rendered still more irregular by the intrusion of a smaller ring-plain. On the N.E. side of the floor stands a very bright little crater and two others on the S. of the centre, each with central mountains.

FERMAT.—An irregular ring-plain 25 miles in diameter on the W. of Sacrobosco. Its partially terraced wall is broken on the N. by a gap which communicates with the interior of a smaller formation. There are some low hills on the floor, which is depressed 6000 feet below the crest of the border.

AZOPHI.—A prominent ring-plain, 30 miles in diameter, E.N.E. of Sacrobosco, its lofty barrier towering nearly 11,000 feet above a somewhat dusky interior, which includes some light spots. A massive curved mountain arm runs from the S. side of this formation to a small ring-plain W. of Playfair.

ABENEZRA.—When observed near the morning terminator, this noteworthy ring-plain, 27 miles in diameter, seems to be divided into two by a curved ridge which traverses the formation from N. to S., and extends beyond its limits. The irregular border rises on the W. to a height of more than 14,000 feet above the deeply-sunken floor, which includes several craters, hills, and ridges.

APIANUS.—A magnificent ring-plain, 38 miles in diameter, N.W. of Aliacensis, with lofty terraced walls, rising on the N.E. to about 9000 feet above the interior, and crowned on the W. by three large conspicuous craters. The border is broken on the N. by a smaller depression and a large ring with low walls. The dark-grey floor appears to be devoid of conspicuous detail.

PLAYFAIR.—A ring-plain, 28 miles in diameter, with massive walls. It is situated on the N. of Apianus, and is connected with it by a mountain arm. The rampart is tolerably continuous, but varies considerably in altitude, rising on the S. to a height of more than 8000 feet above the interior. On the E., extending towards Blanchinus, is a magnificent unnamed formation, bounded on the E. by a broad lofty rampart flanking Blanchinus, Lacaille, Delaunay, and Faye; and on the W. by Playfair and the mountain arm just mentioned. It is fully 60 miles in length from N. to S. Sunrise on this region affords a fine spectacle to the observer with a large telescope. The best phase is when the morning terminator intersects Aliacensis, as at this time the long jagged shadows of the E. wall of Playfair and of the mountain arm are very prominent on the smooth, greyish-blue surface of this immense enclosure.

PONTANUS.—An irregular ring-plain, 28 miles in diameter, S.S.W. of Azophi, with a low broken border, interrupted on the S.W. by a smaller ring-plain, which forms one of a group extending towards the S.W. The dark floor includes a central mountain.

ALIACENSIS.—This ring-plain, 53 miles in diameter, with its neighbour Werner on the N.E., are beautiful telescopic objects under a low sun. Its lofty terraced border rises at one peak on the E. to the tremendous height of 16,500 feet, and at another on the opposite side to nearly 12,000 feet above the floor. The wall on the S. is broken by a crater, and on the W. traversed by narrow passes. There is also a prominent crater on the inner slope of the N.E. wall. The floor includes a small mountain, several little hills, and a crater.

WERNER.—A ring-plain, 45 miles in diameter, with a massive rampart crowned by peaks almost as lofty as any on that of Aliacensis, and with terraces fully as conspicuous. It has a magnificent central mountain, 4500 feet high. At the foot of the N.E. wall Madler observed a small area, which he describes as rivalling the central peak of Aristarchus in brilliancy. Webb, however, was unable to confirm this estimate, though he noted it as very bright, and saw a minute black pit and narrow ravine within it. Neison subsequently found that the black pit is a crater-cone. It would perhaps be rash, with our limited knowledge of minute lunar detail, to assert that Madler over-estimated the brightness of this area, which may have been due to a recent deposit round the orifice of the crater-cone.

POISSON.—An irregular formation on the W. of Aliacensis, extending about 50 miles from W. to E., but much less in a meridional direction. Its N. limits are marked by a number of overlapping ring-plains and craters, and it is much broken elsewhere by smaller depressions. The E. wall is about 7000 feet in height.

GEMMA FRISIUS.—A great composite walled-plain, 80 miles or more in length from N. to S., with a wall rising at one place nearly 14,000 feet above the floor. It is broken on the N. by two fine ring-plains, each about 20 miles in diameter, and on the E. by a third open to the E. There is a central mountain, and several small craters on the floor, especially on the W. side.

BUSCHING.—A ring-plain S. of Zagut, about 36 miles in diameter, with a moderately high but irregular wall. There are several craterlets within and some low hills.

BUCH.—Adjoins Busching on the S.E. It is about 31 miles in diameter, and has a less broken barrier. There is a large crater on the E. wall, and another smaller one on the S.W. Schmidt shows nothing on the floor, but Neison noted two minute crater-cones.

MAUROLYCUS.—This unquestionably ranks as one of the grandest walled- plains on the moon's visible surface, and when viewed under a low sun presents a spectacle which is not easily effaced from the mind. Like so many of the great enclosures in the fourth quadrant, it impresses one with the notion that we have here the result of the crowding together of a number of large rings which, when they were in a semi-fluid or viscous condition, mutually deformed each other. It extends fully 150 miles from E. to W., and more from N. to S.; so it may be taken to include an area on the lunar globe which is, roughly speaking, equal to half the superficies of Ireland. This vast space, bounded by one of the loftiest, most massive, and prominently-terraced ramparts, includes ring-plains, craters, crater-rows, and valleys,—in short, almost every type of lunar formation. It towers on the E. to a height of nearly 14,000 feet above the interior, and on the W., according to Schmidt, to a still greater altitude. A fine rill-valley curves round the outer slope of the W. wall, just below its crest, which is an easy object in a 8 1/2 inch reflector when the opposite border is on the morning terminator, and could doubtless be seen in a smaller instrument; and there is an especially brilliant crater on the S. border, which is not visible till a somewhat later stage of sunrise. The central mountain is of great altitude, its loftiest peaks standing out amid the shadow long before a ray of sunlight has reached the lower slopes of the walls. It is associated with a number of smaller elevations. I have seen three considerable craters and several smaller ones in the interior.

BAROCIUS.—A massive formation, about 50 miles in diameter, on the S.W. side of Maurolycus, whose border it overlaps and considerably deforms. Its wall rises on the E. to a height of 12,000 feet above the floor, and is broken on the N.W. by two great ring-plains. On the inner slope of the S.E. border is a curious oblong enclosure. There is nothing remarkable in the interior. On the dusky grey plain W. of Maurolycus and Barocius there is a number of little formations, many of them being of a very abnormal shape, which are well worthy of examination. I have seen two short unrecorded clefts in connection with these objects.

STOFLER.—A grand object, very similar in size and general character to Maurolycus, its neighbour on the W. To view it and its surroundings at the most striking phase, it should be observed when the morning terminator lies a little E. of the W. wall. At this time the jagged, clean-cut, shadows of the peaks on Faraday and the W. border, the fine terraces, depressions, and other features on the illuminated section of the gigantic rampart, and the smooth bluish-grey floor, combine to make a most beautiful telescopic picture. At a peak on the N.E., the wall attains a height of nearly 12,000 feet, but sinks to a little more than a third of this height on the E. It is apparently loftiest on the N. The most conspicuous of the many craters upon it is the bright deep circular depression E. on the S. wall, and another, rather larger and less regular, on the N.W., which has a very low rim on the side facing the floor, and a craterlet on either side of the apparent gap. A large lozenge-shaped enclosure abuts on the wall, near the crater E., with a border crowned by a number of little peaks, which at an early stage of sunrise resemble a chaplet of pearls. The floor of Stofler is apparently very level, and in colour recalls the beautiful steel-grey tone of Plato seen under certain conditions. I have noted several distinct little craters on its surface, mostly on the N.E. side; and on the E. side a triangular dark patch, close to the foot of the wall, very similar in size and appearance to those within Alphonsus.

FARADAY.—A large ring-plain, about 35 miles in diameter, overlapping the S.W. border of Stofler; its own rampart being overlapped in its turn by two smaller ring-plains on the S.E., and by two still smaller formations (one of which is square-shaped) on the N.W. The wall is broad and very massive on the E. and N.E., prominently terraced, and includes many brilliant little craters. Schmidt shows a ridge and several craters in the interior.

LICETUS.—An irregular formation, about 50 miles in maximum width, on the S. of Stofler, with the flanks of which it is connected by a coarse valley. Neison points out that it consists of a group of ring-plains united into one, owing to the separating walls having been partially destroyed. This seems to be clearly the case, if Licetus is examined under a low sun. On the E. side of the N. portion of the formation, the wall rises to nearly 13,000 feet.

FERNELIUS.—A ring-plain, about 30 miles in diameter, abutting on the N. wall of Stofler. It is overlapped on the E. by another similar formation of about half its size. There are many craters and depressions on the borders of both, and a large crater between the smaller enclosure and the N.E. outer slope of Stofler. Schmidt shows eight craters on the floor of Fernelius.

NONIUS.—A ring-plain, about 20 miles in diameter, abutting on the N. wall of Fernelius. There is a prominent bright crater on the W. of it, and another on the N., from which a delicate valley runs towards the W. side of Walter.

CLAIRAUT.—A very peculiar formation, about 40 miles in diameter, S. of Maurolycus, affording another good example of interference and overlapping. The continuity of its border, nowhere very regular, has been entirely destroyed on the S. by the subsequent formation of two large rings, some 10 or 12 miles in diameter, the more easterly of which has, in its turn, been partially wrecked on the N. by a smaller object of the same class. There is also a ring-plain N.E. of Clairaut, which has very clearly modified the shape of the border on this side. Two craters on the floor of Clairaut are easy objects.

BACON.—A very fine ring-plain, 40 miles in diameter, S.W. of Clairaut. At one peak on the E. the terraced wall rises to nearly 14,000 feet above the interior. It is broken on the S. by three or four craters. On the W. there is an irregular inconspicuous enclosure, whose contiguity has apparently modified the shape of the border. There are two large rings on the N. (the more easterly having a central peak), and a third on the E. The floor appears to be devoid of prominent detail.

CUVIER.—A walled-plain, about 50 miles in diameter, on the S.E. of Clairaut. The border on the E. rises to 12,000 feet; and on the N.W. is much broken by depressions. Neison has seen a mound, with a minute crater W. of it, on the otherwise undisturbed interior.

JACOBI.—A ring-plain S. of Cuvier, about 40 miles in diameter, with walls much broken on the N. and S., but rising on the E. to nearly 10,000 feet. There is a group of craters (nearly central) on the floor. The region S. of this formation abounds in large unnamed objects.

LILIUS.—An irregular ring-plain, 39 miles in diameter, with a rampart on the E. nearly 10,000 feet above the floor. A smaller ring between it and Jacobi has considerably inflected the wall towards the interior. It has a conspicuous central mountain.

ZACH.—A massive formation, 46 miles in diameter, on the S. of Lilius, with prominently terraced walls, rising on the E. to 13,000 feet above the interior. A small ring-plain, whose wall stands 6000 feet above the floor, is associated with the N. border. Two other rings, on the S.W. and N.E. respectively, have craters on their ramparts and central hills.

PENTLAND.—A fine conspicuous formation under a low sun, even in a region abounding in such objects. It is about 50 miles in diameter, with a border exceeding in places 10,000 feet in height above the floor, which includes an especially fine central mountain.

KINAU.—One of the group of remarkable ring-plains extending in a N.W. direction from Pentland.

SIMPELIUS.—Another grand circumvallation, almost as large as Pentland, but unfortunately much foreshortened. One of its peaks on the E. rises to a height of more than 12,000 feet above the floor, on which there is a small central mountain. Between Simpelius and Pentland are several ring- plains, most of which appear to have been squeezed and deformed into abnormal shapes.

CURTIUS.—A magnificent formation, about 50 miles in diameter, with one of the loftiest ramparts on the visible surface, rising at a mountain mass on the N.E. to more than 22,000 feet, an altitude which is only surpassed by peaks on the walls of Newton and Casatus. There is a bright crater on the S.E. border and another on the W. The formation is too near the S. limb for satisfactory scrutiny. Between Curtius and Zach is a fine group of unnamed enclosures.

APPENDIX

DESCRIPTION OF THE MAP

The accompanying map, eighteen inches in diameter, represents the moon under mean libration. Meridian lines and parallels of latitude are drawn at every 10 deg., except in the case of the meridians of 80 deg. E. and W. longitude, which are omitted to avoid confusion, and as being practically needless. These lines will enable the observer, with the aid of the Tables in the Appendix, to find the position of the terminator at any time required. As astronomical telescopes exhibit objects inverted, maps of the moon are always drawn upside down, and with the right and left interchanged, as in the diagram above, which also shows how the quadrants are numbered.

This circle [drawing of circle], intended to be .15708 in diameter, represents a circle of one degree in diameter at the centre of the map, and as the length of one selenographical degree is 18.871 miles, it represents an area of nearly 280 square miles.

The catalogue is so arranged that, beginning with the W. limb, and referring to the lists under the first and fourth, and the second and third quadrants, all the formations falling within the meridians 90 deg. to 60 deg., 60 deg. to 40 deg., 40 deg. to 20 deg., 20 deg. to 0 deg. (the central meridian), and from 0 deg. to 20 deg., and so on, to the E. limb, will be found in convenient proximity in the text.

In the Catalogue, N. S. E. W. are used as abbreviations for the cardinal points.

LIST OF THE MARIA, OR GREY PLAINS, TERMED "SEAS," &c.

FIRST QUADRANT.

Mare Tranquilitatis (nearly the whole), page 5. ,, Foecunditatis (the N. portion), 5. ,, Serenitatis, 5. ,, Crisium, 6. ,, Frigoris (a portion), 5. ,, Vaporum (nearly the whole), 6. ,, Humboldtianum, 6. ,, Smythii (a portion), 39. Lacus Mortis, 53. ,, Somniorum. Palus Somnii. ,, Nebularum (a portion), 62. ,, Putredinis, 61. Sinus Medii (a portion), 6.

SECOND QUADRANT.

Mare Imbrium, 5. ,, Nubium (the N. portion), 5. ,, Frigoris (a portion), 5. ,, Vaporum (a portion), 6. Oceanus Procellarum (the N. portion), 5. Palus Nebularum (a portion), 62. Sinus Iridum, 80. ,, Medii (a portion), 6. ,, Roris, 90. ,, Aestuum.

THIRD QUADRANT.

Mare Nubium (the greater portion), 5. ,, Humorum, 6. Oceanus Procellarum (the S. portion), 5. Sinus Medii (a small portion), 6.

FOURTH QUADRANT.

Mare Foecunditatis (the greater portion), 5. ,, Nectaris, 7. ,, Tranquilitatis (a small portion), 5. ,, Australe, 127. ,, Smythii (a portion), 39. Sinus Medii (a portion), 6.

LIST OF SOME OF THE MOST PROMINENT MOUNTAIN RANGES, PROMONTORIES, ISOLATED MOUNTAINS, AND REMARKABLE HILLS.

FIRST QUADRANT.

The Alps. The western portion of the range.

The Apennines. The extreme northern part of the range.

The Caucasus.

The Haemus.

The Taurus.

The North Polar Range. On the limb extending from N. lat. 81 deg. towards the E.

The Humboldt Mountains. On the limb from N. lat. 72 deg. to N. lat. 53 deg.

Mount Argaeus. A mountain mass rising some 8000 feet above the Mare Serenitatis in N. lat. 20 deg., W. long. 28 deg., N.W. of Dawes.

Prom. Acherusia. A bright promontory at the W. extremity of the Haemus range, rising nearly 5000 feet above the Mare Serenitatis. N. lat. 17 deg., W. long. 22 deg.

Cape Agarum. The N. end of a projecting headland on the S.W. side of the Mare Crisium, in N. lat. 14 deg., W. long. 66 deg., rising nearly 11,000 feet above the Mare.

Le Monnier A. An isolated mountain more than 3000 feet high, standing about midway between the extremities of the bay: probably a relic of a once complete ring.

Secchi. South of this formation there is a lofty prominent isolated mountain.

Manilius A and beta. Two conspicuous mountains N. of Manilius; A, the more westerly, being more than 5000 feet, and beta about 2000 feet in height.

Autolycus A. A mountain of considerable altitude, S. of this formation.

Mont Blanc. Principal peak, N. lat. 46 deg., W. long. 0 deg. 30 min., nearly 12,000 feet in height.

Cassini epsilon and delta. Two adjoining mountain masses N. of Cassini, more than 5000 feet high.

Eudoxus. S.E. of this formation, in N. lat. 43 deg., W. long. 10 deg., are two bright mountain masses, the more southerly rising 7000, and the other 4000 feet above the surface.

Mount Hadley. The northern extremity of the Apennines, in N. lat. 27 deg. W. long. 5 deg., rising more than 15,000 feet above the Mare.

Mount Bradley. A promontory of the Apennines, in N, lat. 23 deg., W. long. 1 deg., nearly 14,000 feet above the Mare Imbrium.

The Silberschlag Range, running from near the S.E. side of Julius Caesar to the region W. of Agrippa.

SECOND QUADRANT.

The Alps. The eastern and greater portion.

The Apennines. Nearly the whole of the range.

The Carpathians.

The Teneriffe Mountains. S.E. of Plato. Highest peak, 8000 feet.

The Straight Range. East of the last, in N. lat. 48 deg., E. long. 20 deg.

The Harbinger Mountains. N.W. of Aristarchus.

The Hercynian Mountains. Near the N.E. limb, E. of Otto Struve, N. lat. 25 deg.

Mount Huygens. A mountain mass projecting from the escarpment of the Apennines, in N. lat. 20 deg., E. long. 3 deg., one peak rising to 18,000 feet above the Mare Imbrium.

Mount Wolf. A great square-shaped mountain mass, near the S.E. extremity of the Apennines, in N. lat. 17 deg., E. long. 9 deg., the loftiest peak rising to nearly 12,000 feet above the Mare Imbrium.

Eratosthenes I and X. Two isolated mountains N. of this formation, in N. lat. 20 deg.; X is 1800 feet in height.

Pico. A magnificent isolated mountain, S. of Plato, in N. lat. 45 deg., E. long. 9 deg., rising some 8000 feet above the Mare Imbrium.

Pico B. A triple-peaked mountain a few miles S. of Pico.

Piton. A bright isolated mountain 7000 feet high, in N. lat. 1 deg., E. long. 1 deg.

Fontinelle A. A conspicuous isolated mountain about 3000 feet high, S. of Fontinelle.

Archimedes Z. A triangular-shaped group E. of Archimedes, in N. lat. 31 deg., E. long. 8 deg., the highest of the peaks rising more than 2000 feet.

Caroline Herschel. E. of this formation is a double-peaked mountain rising to 1300 feet.

Gruithuisen delta and gamma. On the N. of this bright crater, in N. lat. 36 deg., E. long. 40 deg., rises a fine mountain, delta, nearly 6000 feet in height, and on the N.E. of it the larger mass gamma, almost as lofty.

Mairan. There is a group of three bright little mountains, the loftiest about 800 feet above the Mare, some distance E. of this formation.

Euler beta. A fine but small mountain group, more than 3600 feet high, on the Mare Imbrium, S.E. of Euler.

The Laplace Promontory. A magnificent headland on the N. side of the Sinus Iridum, rising about 9000 feet above the latter, and about 7000 feet above the Mare Imbrium.

Cape Heraclides. A fine but less prominent headland on the opposite side of the bay, rising more than 4000 feet above it.

Lahire. A large bright isolated mountain in the Mare Imbrium, N.E. of Lambert, in N. lat. 27 deg., E. long. 25 deg. It is, according to Schroter, nearly 5000 feet high.

Delisle beta. A curious club-shaped mountain on the S.E. of this formation, nearly 4000 feet in height.

Pytheas beta. An isolated mountain, 900 feet high, in N. lat. 20 deg., E. long. 23 deg.

Kirch. There is a small isolated hill a few miles N. of this formation.

Kirch GAMMA. A bright mountain about 700 feet high, in N. lat. 39 deg., E. long. 3 deg.

Piazzi Smyth beta. A small bright isolated mountain on a ridge S. of this, is a noteworthy object under a low sun.

Lambert GAMMA. In N. lat. 26 deg., E. long. 18 deg.; a remarkable curved mountain about 3000 feet in height, a brilliant object under a low sun.

D'Alembert Mountains. A range on the E. limb running S. from N. lat. 12 deg.

Wollaston. An isolated triangular mountain about midway between this and Wollaston B.

THIRD QUADRANT.

The Riphaean Mountains. An isolated range S. of Landsberg in S. lat. 7 deg., E. long. 28 deg. They run in a meridional direction, and rise at one peak to nearly 3000 feet above the Oceanus Procellarum.

The Percy Mountains extend from the eastern flank of Gassendi towards Mersenius, forming the north-eastern border of the Mare Humorum.

Prom. Aenarium. A steep bluff situated at the northern end of a plateau, some distance E. of Arzachel, in S. lat. 18 deg., E. long. 9 deg. It rises some 2000 feet above the Mare Nubium.

Euclides zeta and chi. Two mountain masses N. of this formation in S. lat. 5 deg.; zeta rises about 1700 feet above the Mare; both are evidently offshoots from the Riphaean range.

Landsberg H. An isolated hill in S. lat. 4 deg., E. long. 25 deg.

Nicollet C. S.E. of Nicollet, in S. lat. 22 deg., E. long. 17 deg.; is hemmed in by a mountain mass rising to more than 2000 feet above the Mare Nubium.

The Stag's-Horn Mountains. At the S. end of the straight wall, or "railroad," in S. lat. 24 deg., E. long. 8 deg., a curious mountain mass rising about 2000 feet above the Mare Nubium.

Lacroix delta. A mountain more than 7000 feet high, N. of Lacroix.

Flamsteed E. A mountain of more than 3000 feet in S. lat. 4 deg., E. long. 51 deg.

D'Alembert Mountains. A very lofty range on the E. limb, extending to S. lat. 11 deg.

The Cordilleras. Close to the E. limb; they lie between S. lat. 8 deg. and S. lat. 23 deg.

Rook Mountains. On the E. limb, extending from about S. lat. 18 deg. to S. lat. 35 deg. According to Schroter, they attain a height of 25,000 feet.

Dorfel Mountains. On the S.E. limb between S. lat. 57 deg. and S. lat. 80 deg.

Leibnitz Mountains. On the S. limb extending W. from S. lat. 80 deg. beyond the Pole on to the Fourth Quadrant. Perhaps the loftiest range on the limb. Madler's measures give more than 27,000 feet as the height of one peak, and there are several others nearly as high.

FOURTH QUADRANT.

The Altai Mountains. A fine conspicuous serpentine range, extending from the E. side of Piccolomini in a north-easterly direction to the region between Tacitus and Catherina, a length of about 275 miles. The loftiest peak is over 13,000 feet. The average height of the southern portion is about 6000 feet. The region lying on the S.E. of this range is a vast tableland, devoid of prominent objects, rising gradually towards the mountains, which shelve rapidly down to an equally barren expanse on the N.W.

The Pyrenees. These mountains, on the E. of Guttemberg, border the western side of the Mare Nectaris. Their loftiest peak, rising nearly to 12,000 feet, is on the S.E. of Guttemberg.

LIST OF THE PRINCIPAL RAY-SYSTEMS, LIGHT-SURROUNDED CRATERS, AND LIGHT- SPOTS.

[In this list, which does claim to be exhaustive, most of the objects noted by Schmidt are incorporated.]

FIRST QUADRANT.

Autolycus. Encircled by a delicate nimbus, throwing out four or five prominent rays extending towards Archimedes. Seen best under evening illumination.

Aristillus. The centre of a noteworthy system of delicate rays extending W. towards the Caucasus; and on the S. disappearing among the rays of Autolycus. They are traceable on the Mare Nubium near Kirch.

Theaetetus. A very brilliant group of little hills E. of this formation.

Eudoxus A. A light-surrounded crater W. of Eudoxus, with distinct long streaks, one of which extends to the S. wall of Aristoteles.

Aristoteles A. A light-surrounded crater in the Mare Frigoris, N.E. of Aristoteles.

Aratus. A very conspicuously brilliant crater in the Apennines, with a smaller light-surrounded crater W. of it.

Sulpicius Gallus. A light spot near.

Manilius. Surrounded by a light halo and streaks.

Taquet. Has a prominent nimbus, and indications of very delicate streaks.

Plinius A. Is surrounded by a well-marked halo.

Posidonius gamma. Among the hills E. of this formation a light spot resembling Linne, according to Schmidt. He first saw it in 1867, when it had a delicate black spot in the centre. Dr. Vogel observed and drew it in 1871 with the great refractor at Bothkamp. These observations were confirmed by Schmidt in 1875 with the 14-feet refractor at Berlin.

Littrow. A very bright light-spot with streaks, on the site of a little crater and well-known cleft E. of this ring-plain.

Romer. A light-surrounded mountain on the E.

Macrobius. Two light-surrounded craters on the E. of this formation, the more northerly being the brighter.

Cleomedes A. (On the floor.) Surrounded by a nimbus and rays. Large crater, A, on the E. has also a nimbus and rays.

Agrippa. Exhibits faint rays.

Godin. Exhibits faint rays.

Proclus. A well-known ray-centre, some of the rays prominent on part of the Mare Crisium.

Taruntius. Has a very faint nimbus, with rays, on a dark surface.

Dionysius. A brilliant crater with a prominent, bright, excentrically placed nimbus on a dark surface, on which distinct rays are displayed.

Hypatia B. A very small bright crater on a dark surface: surrounded by a faint nimbus.

Apollonius. Among the hills S. of this, there is a small bright streak system.

Eimmart. There is a large white spot N.W. of this.

Geminus is associated with a system of very delicate rays.

Menelaus. A brilliant object. It is traversed by a long ray from Tycho.

SECOND QUADRANT.

Anaxagoras. The centre of an important ray-system.

Timocharis is surrounded by a pale irregular nimbus and faint rays, most prominently developed on the W. side of the formation.

Copernicus. Next to Tycho, the most extended ray-centre on the visible surface. Some distance on the E., in E. long. 25 deg., N. lat. 11 deg., lies a very small but conspicuous system, and in E. long. 22 deg., N. lat. 8 deg. a bright light spot among little hills.

Gambart A. A bright crater with large nimbus and rays.

Landsberg A. A light-surrounded crater on a dark surface, with companions, referred to under the Third Quadrant.

Encke. There is a light-surrounded crater S. of this.

Kepler. A noted ray-centre. It is surrounded by an extensive halo, especially well developed on the E., across the Mare Procellarum.

Bessarion. Two bright craters: the more northerly is prominently light-surrounded, while its companion is less conspicuously so.

Aristarchus.—The most conspicuous bright centre on the moon, the origin of a complicated ray-system.

Delisle. S. of this formation there is a tolerably bright spot on the site of some hills.

Timaeus. A ray-centre.

Euler. Feeble halo with streaks.

Galileo. Between this and Reiner is a curious bright formation with short rays, referred to in the Catalogue, under Reiner.

Cavalerius. A light streak originating in the W. wall, and extending on to the Oceanus Procellarum.

Olbers. A considerable ray-system, but seldom distinctly visible.

Lichtenberg. Faintly light-surrounded.

THIRD QUADRANT.

Tycho. The largest and best known system on the visible surface.

Zuchius. A remarkable ray-system, but one which is only well seen when libration is favourable.

Bailly. N. of the centre of this great enclosure are two very distinct radiating streaks.

Schickard. Four conspicuous light spots, probably craters, on the S.E.

Byrgius A. A brilliant ray-centre, most of the rays trending eastward from a nimbus.

Hainzel. There are several bright spots E. of this formation.

Mersenius. Two or three light-rays originate from a point on the W. rampart.

Mersenius C. A light-surrounded crater with short rays.

Grimaldi. There are three bright spots on the W. wall.

Damoiseau. A light-surrounded crater W. of Damoiseau, E. long. 58 deg., S. lat. 6 deg.

Flamsteed C. A light-surrounded crater on a dark surface.

Lubieniezky A. Crater with halo on a dark surface.

Lubieniezky F. Crater with halo on a dark surface.

Lubieniezky G. Crater with halo on a dark surface.

Birt a. A light-surrounded crater.

Landsberg. E. of Landsberg, four light-surrounded craters, forming with Landsberg A (in the Second Quadrant) an interesting group.

Lohrmann A. A light-surrounded crater, with a light area a few miles N. of it. S. lat. 1 deg., E. long. 61 deg.

Euclides. Has a conspicuous nimbus with traces of rays, a typical example.

Guerike. There is a crater, with nimbus, W. of this, in E. long. 12 deg., S. lat. 11 deg. 5 min.

Parry. A very brilliant light-spot in the S. wall.

Parry A. Surrounded by a bright nimbus.

Alpetragius B. A conspicuous light-surrounded crater, one of the most remarkable on the moon.

Alpetragius d (E. long. 11 deg., S. lat. 13 deg. 8 min.). A bright spot, seen by Madler as a crater, but which, as Schmidt found in 1868, no longer answers to this description.

Mosting C. A light-surrounded crater.

Lalande. Has a large nimbus and distinct rays.

Hell. A large ill-defined spot in E. long. 4 deg., S. lat. 33 deg. This is most probably the site of the white cloud seen by Cassini.

Mercator. There is a brilliant crater and light area under E. wall.

FOURTH QUADRANT.

Stevinus a. A crater E. of Stevinus; it is a centre of wide extending rays.

Furnerius A. Prominently light-surrounded, with bright streaks, radiating for a long distance N. and S.

Messier A. The well-known "Comet" rays, extending E. of this.

Langrenus. Has a large but very pale ray-system. It is best seen under a low evening sun. Three long streaks radiate towards the E. from the foot of the glacis of the S.E. wall.

Censorinus. A very brilliant crater with faint rays.

Theophilus. The central mountain is faintly light-surrounded.

Madler. This ring-plain and the neighbourhood on the N. and N.W., include many bright areas and curious streaks.

Almanon. About midway between this and Argelander is a very brilliant little crater.

Beaumont. Between this and Cyrillus stand three considerable craters with nimbi.

Cyrillus A. A prominent light-surrounded crater.

Alfraganus. A light-surrounded crater with rays.

POSITION OF THE LUNAR TERMINATOR

Though the position of the Lunar Terminator is given for mean midnight throughout the year in that very useful publication the Companion to the Observatory, it is frequently important in examining or comparing former drawings and observations to ascertain its position at the times when they were made. For this purpose the subjoined tables (which first appeared in the Selenographical Journal) will be found useful, as they give for any day between A.D. 1780 and A.D. 1900 the selenographical longitude of the point where the terminator crosses the moon's equator, which it does very nearly at right angles.

[Tables and examples]

LUNAR ELEMENTS

Moon's mean apparent diameter - 31 min. 8 sec.

Moon's maximum apparent diameter - 33 min. 33.20 sec.

Moon's minimum apparent diameter - 29 min. 23.65 sec.

Moon's diameter, in miles - 2163 miles.

Volume (earth's = 1) - 1/49.20 or 0.02033.

Mass (earth's = 1) - 1/81.40 or 0.0128.

Density (earth's = 1) - 0.60419, or 3.444 the density of water (water being unity).

Surface area, about 14,600,000 square miles (earth's surface area, 196,870,000 miles)

Earth's surface area = 1, moon's - About 2/27 or 0.07407.

Action of gravity at surface - 0.16489 or 1/6.065 of the earth's.

Surface of moon never seen - 0.4100.

Surface of moon seen at one time or another - 0.5900.

Synodical revolution, or interval from new moon to new moon (commonly called a lunation) - 29 d. 12 h. 44 m. 2.684 s. - 29.5305887 days.

Sidereal revolution, or time taken in passing from one star to the same star again - 27 d. 7 h. 43 m. 11.545 s. - 27.3216614 days.

Tropical revolution, or time taken in passing from "the first point of Aries" to the same point again - 27 d. 7 h. 43 m. 4.68 s. - 27.321582 days.

Anomalistic revolution, or time taken in passing from perigee to perigee - 27 d. 13 h. 18 m. 37.44 s. - 27.55460 days.

Nodical revolution, or time taken in passing from rising node to rising node - 27 d. 5h. 5m. 35.81 s. - 27.21222 days.

Distance (mean) in terms of the equatorial radius of the earth - 60.27.

Distance in miles (mean) - 238,840 miles.

Distance, maximum - 252,972 miles.

Distance, minimum - 221,614 miles.

Mean excentricity of moon's orbit - 0.05490807.

Inclination of moon's orbit to the ecliptic (mean) - 5 deg. 8 min. 39.96 sec.

Inclination of moon's axis to the ecliptic - 87 deg. 27 min. 51 sec.

Inclination of moon's equator to the ecliptic - 1 deg. 32 min. 9 sec.

Maximum libration in latitude - 6 deg. 44 min.

Maximum libration in longitude - 7 deg. 45 min.

Maximum total libration from earth's centre - 10 deg. 16 min.

Maximum diurnal libration - 1 deg. 1 min. 28.8 sec.

Angle subtended by one degree of selenographical latitude and longitude at the centre of the moon's disc, when at its mean distance - 16.566 sec.

Length of a degree under these conditions - 18.871 miles.

Selenographical arc at the centre of the moon's surface, subtending an angle of one second of arc - 3 min. 37.31 sec.

Miles at the centre of the moon's disc, subtending an angle of one second of arc - 1.139

[It must be remembered that this value is increased, in departing from the centre, in the proportion of the secants of the angular distance from the centre.]

Period of similar phase - 59 d. 1h. 28m. = 2 lunations.

Or, more accurately - 442 d. 23 h. = 15 lunations.

THE END