Part 5

EIMMART.--A conspicuous ring-plain with bright walls on the N.W. margin of the Mare Crisium. The E. border attains a height of 10,000 feet above the interior, which, according to Schmidt, has a small central mountain. There is a rill-like valley on the E. of the formation.

ORIANI.--An irregular object, 32 miles in diameter, somewhat difficult to identify, N.W. of the last. There is a conspicuous crater on the N. of it, with which it is connected by a prominent ridge.

PLUTARCH.--A fine ring-plain W. of Oriani, with regular walls, and, according to Neison, with two central mountains, only one of which I have seen. Both this formation and the last are beautifully shown in a photograph taken August 19, 1891, at the Lick Observatory, when the moon's age was 15 d. 10 hrs.

SENECA.--Rather smaller than Plutarch. Too near the limb for satisfactory observation. Schmidt shows two considerable mountains in the interior. The position of this object in Schmidt's chart is not accordant with its place in Beer and Madler's map, nor in that of Neison.

HAHN.--A ring-plain, 46 miles in diameter, with a fine central mountain and lofty peaks on the border, which is not continuous on the S. There is a large and prominent crater on the E.

BEROSUS.--A somewhat smaller object of a similar type, N. of Hahn, but with a loftier wall. There is a want of continuity also in the border, the eastern and western sections of which, instead of joining, extend for some distance towards the S., forming a narrow gorge or valley. Outside the S.E. wall there is a small crater, and some irregular depressions on the E. The minute central mountain is only seen with difficulty under a low evening sun. The bright region between Hahn and Berosus and the western flank of Cleomedes is an extensive plain, devoid of prominent detail, and which, according to Neison, includes an area of 40,000 square miles.

GAUSS.--A large, and nearly circular walled-plain, 111 miles in diameter, situated close to the N.W. limb, and consequently always foreshortened into a more or less elongated ellipse. But for this it would be one of the grandest objects in the first quadrant. Under the designation of "Mercurius Falsus" it received great attention from Schroter, who gives several representations of it in his Selenotopographische Fragmente, which, though drawn in his usual conventional style, convey a juster idea of its salient features than many subsequent drawings made under far better optical conditions. The border, especially on the W., is very complex, and is discontinuous on the S., where it is intersected by more than one pass, and is prolonged far beyond the apparent limits of the formation. The most noteworthy feature is the magnificent mountain chain which traverses the floor from N. to S. It is interesting to watch the progress of sunset thereon, and see peak after peak disappear, till only the great central boss and a few minute glittering points of light, representing the loftier portions of the chain, remain to indicate its position. Madler expatiates on the sublime view which would be obtained by any one standing on the highest peak and observing the setting sun on one side of him and the nearly "full" earth on the other; while beneath him would lie a vast plain, shrouded in darkness, surrounded by the brilliantly illuminated peaks on the lofty border, gradually passing out of sunlight. In addition to the central mountain range, there are some large rings, craters, hillocks, &c., on the floor; and on the inner slope of the W. border there is a very large circular enclosure resembling a ring-plain, not recorded in the maps. Schmidt shows a row of large craters on the outer slope of the E. border. Of these, one is very conspicuous under a low evening sun, by reason of its brilliant walls and interior. In the region between Gauss and Berosus is a number of narrow steep ridges which follow the curvature of the E. wall.

STRUVE.--A small irregularly-shaped formation, open towards the S., forming one of the curious group of unsymmetrical enclosures associated with Messala. Its dark floor and a small dusky area on the N. indicate its position under a high sun.

CARRINGTON.--A small ring-plain, belonging to the Messala group, adjoining Schumacher on the N.W.

MERCURIUS.--This formation is 25 miles in diameter. A small crater stands on the S.E. section of the wall. There is a longitudinal range in the interior, and on the W. and N.W. the remains of two large walled-plains, the more westerly of which is a noteworthy object under suitable conditions. A short distance S. is a large, irregular, and very dark marking. On the N., lies an immense bright plain, extending nearly to the border of Endymion.

WEST LONGITUDE 60 deg. TO 40 deg.

TARUNTIUS.--Notwithstanding its comparatively low walls, this ring-plain, 44 miles in diameter, is a very conspicuous object under a rising sun. Like Vitello and a few other formations, it has an inner ring on the floor, concentric with the outer rampart, which I have often seen nearly complete under evening illumination. There is a small bright crater on the S.E. wall, and a larger one on the crest of the N.E. wall, with a much more minute depression on the W. of it, the intervening space exhibiting signs of disturbance. The upper portion of the wall is very steep, contrasting in this respect with the very gentle inclination of the glacis, which on the S. extends to a distance of at least 30 miles before it sinks to the level of the surrounding country, the gradient probably being as slight as 1 in 45. Two low dusky rings and a long narrow valley with brilliant flanks are prominent objects on the plain E. of Taruntius under a low evening sun.

SECCHI.--A partially enclosed little ring-plain S. of Taruntius, with a prominent central mountain and bright walls. There is a short cleft running in a N.E. direction from a point near the E. wall. Schmidt represents it as a row of inosculating craters.

PICARD.--The largest of the craters on the surface of the Mare Crisium, 21 miles in diameter. The floor, which includes a central mountain, is depressed about 2000 feet below the outer surface, and is surrounded by walls rising some 3000 feet above the Mare. A small but lofty ring-plain, Picard E, on the E., near the border of the Mare, is remarkable for its change of aspect under different angles of illumination. A long curved ridge running S. from this, with a lower ridge on the west, sometimes resemble a large enclosure with a central mountain. Still farther S., there is another bright deep crater, a, with a large low ring adjoining it on the S., abutting on the S.E. border of the Mare. Schroter bestowed much attention on these and other formations on the Mare Crisium, and attributed certain changes which he observed to a lunar atmosphere.

PEIRCE.--This formation, smaller than Picard, is also prominent, its border being very bright. There is a central peak, which, though not an easy object, I once glimpsed with a 4 inch Cook achromatic, and have seen it two or three times since with an 8 1/2 inch Calver reflector. A small crater, detected by Schmidt, which I once saw very distinctly under evening illumination, stands on the floor at the foot of the W. wall. Peirce A, a deeper formation, lies a little N. of Peirce, and has also, according to Neison, a very slight central hill, which is only just perceptible under the most favourable conditions. Schmidt appears to have overlooked it.

PROCLUS.--One of the most brilliant objects on the moon's visible surface, and hence extremely difficult to observe satisfactorily. It is about 18 miles in diameter, with very steep walls, and, according to Schmidt, has a small crater on its east border, where Madler shows a break. It is questionable whether there is a central mountain. It is the centre of a number of radiating light streaks which partly traverse the Mare Crisium, and with those emanating from Picard, Peirce, and other objects thereon, form a very complicated system.

MACROBIUS.--This, with a companion ring on the W., is a very beautiful object under a low sun. It is 42 miles in diameter, and is encircled by a bright, regular, but complex border, some 13,000 feet in height above the floor. Its crest is broken on the E. by a large brilliant crater, and its continuity is interrupted on the N. by a formation resembling a large double crater, which is associated with a number of low rounded banks and ridges extending some distance towards the N.W., and breaking the continuity of the glacis. The W. wall is much terraced, and on the N.W. includes a row of prominent depressions, well seen when the interior is about half illuminated under a rising sun. The central mountain is of the compound type, but not at all prominent. The companion ring, Macrobius C, is terraced internally on the W., and the continuity of its N. border broken by two depressions. There is a rill-valley between its N.E. side and Macrobius.

CLEOMEDES.--A large oblong enclosure, 78 miles in diameter, with massive walls, varying in altitude from 8000 to 10,000 feet above the interior. The most noteworthy features in connection with the circumvallation are the prominent depressions on the W. wall. Under a rising sun, when about one-fourth of the floor is in shadow, three of these can be easily distinguished, each resembling in form the analemma figure. There are two other curious depressions at the S.W. end of the formation. On the dark steel-grey floor are two irregular dusky areas, and a narrow but bright central mountain, on which, according to Schmidt, stand two little craters. There are two ring-plains on the S.W. quarter, and a group of three associated craters on the N. side, one of which (A) Schroter believed came into existence after he commenced to observe the formation, a supposition that has been shown by Birt and others to be very improbable.

TRALLES.--A large irregular crater, one of the deepest on the visible surface of the moon, situated on the N.E. wall of Cleomedes. There is a crater on its N. wall, and, according to Schmidt, some ridges and three closely associated craters on the floor.

BURCKHARDT.--This object, situated on an apparent extension of the W. wall of Cleomedes, is 35 miles in diameter, with a lofty border, rising on the E. to an altitude of nearly 13,000 feet. It has a prominent central mountain and some low ridges on the floor, which, together with two minute craters on the S.W. wall, I have seen under a low angle of morning illumination. It is flanked both on the E. and W. by deep irregular depressions, which present the appearance of having once been complete formations.

GEMINUS.--A fine regular ring-plain, 54 miles in diameter, nearly circular, with bright walls, rising on the E. to a height of more than 12,000 feet, and on the opposite side to nearly 16,000 feet above the floor. Their crest is everywhere very steep, and the inner slope is much terraced. There is a small but conspicuous mountain in the interior; N. of which I have seen a long ridge, where Schmidt shows some hillocks. Two fine clefts are easily visible within the ring, one running for some distance on the S.E. side of the floor, mounting the inner slope of the S.W. border to the summit ridge (where it is apparently interrupted), and then striking across the plain in a S.W. direction. Here it is accompanied for a short distance by a somewhat coarser companion, running parallel to it on the N. The other cleft occupies a very similar position on the N.W. side of the floor at the inner foot of the wall. On several occasions, when observing this formation and the vicinity, I have been struck by its peculiar colour under a low evening sun. At this time the whole region appears to be of a warm light brown or sepia tone.

BERNOUILLI.--A very deep ring-plain on the W. side of Geminus. Under evening illumination its lofty W. wall, which rises to a height of nearly 13,000 feet above the floor, is conspicuously brilliant. This formation exhibits a marked departure from the circular type, being bounded by rectilineal sides. The inner slope of the W. wall is slightly terraced. The border on the S. is much lower than elsewhere, as is evident when the formation is on the evening terminator. On the N. is the deep crater Messala a.

NEWCOMB.--The most prominent of a group of formations standing in the midst of the Haemus Mountains. Its crest is nearly 12,000 feet above the floor, on which there are some hills.

MESSALA.--This fine walled-plain, nearly 70 miles in diameter, is, with its surroundings, an especially interesting object when observed under a low angle of illumination. Its complex border, though roughly circular, displays many irregularities in outline, due mainly to rows of depressions. The best view of it is obtained when the W. wall is on the evening terminator. At this phase, if libration is favourable, the manifold details of its very uneven and apparently convex floor are best seen. On the S.W. side is a group of large craters associated with a number of low hills, of which Schmidt shows five; but I have seen many more, together with several ridges between them and the E. wall. I noted also a cleft, or it may be a narrow valley, running from the foot of the N.W. wall towards the centre. On the floor, abutting on the N.E. border, is a semicircular ridge of considerable height, and beyond the border on the N.E. there is another curved ridge, completing the circle, the wall forming the diameter. This formation is clearly of more ancient date than Messala, as the N.E. wall of the latter has cut through it. Where Messala joins Schumacher there is a break in the border, occupied by three deep depressions.

SCHUMACHER.--A large irregular ring-plain, 28 miles in diameter, associated with the N. wall of Messala, and having other smaller rings adjoining it on the E. and N. The interior seems to be devoid of detail.

HOOKE.--Another irregular ring-plain, 28 miles in diameter, on the N.E. of Messala. There is a bright crater of considerable size on the S.W., which is said to be more than 6000 feet in depth, and, according to Neison, is visible as a white spot at full. There is a smaller crater on the slope of the N.W. wall.

SHUCKBURGH.--A square-shaped enclosure on the N. of the last, with a comparatively low border. It has a conspicuous crater at its N.W. corner.

BERZELIUS.--A considerable ring-plain of regular form, with low walls and dark interior, on which there is a central peak, difficult to detect.