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minutlaries of the general parme, howe
the other the first meridian. E. of this point we notice an imperfect ring, Sömmering, touching the equator : N. of this is a somewhat similar object, the Schröter of B. and M., forming the principal feature in “ a labyrinthine mass, the complete disentangling of which could scarcely be successfully accomplished with the most powerful telescope. The countless multitude of hills which fill this landscape appears, even in favourable circumstances, almost like a mere fine luminous dust.” Most of the elevations, however, show connection in chains, affecting a general parallelism with the tolerably distinct boundaries of the district, which consists exclusively of the minutest and most difficult groups. There is no great amount of elevation, especially for the Moon: some points in the outer border of the mass may reach 2600 f. The interior hills are very difficult of measurement: , central, and by far the highest, may lie 2300 f. above a valley 9 miles E. The majority of the eminences range from 1000 down to 130 or even 70 f. The least visible of them lie eastward ; but they are probably steep-sided, as, even when the detail is confused by too high an illumination, they never give the impression of a plain, notwithstanding their grey colour; and this tone may be due to the great multitude of minute and separately undistinguishable shadows. Craters are rare amongst them. Such is the account of B. and M., who add in a note, that notwithstanding their especial care, which they hope a comparison of their Map with the sky will prove, they could never perceive the slightest traces of the fortress-like ramparts which had been so much paraded for a length of time. Lohrmann, they add, had met with no more success; his figure, indeed, was very unlike theirs, but under the circumstances this could not be matter of surprise. Li's design is certainly not merely very dissimilar, but poor in detail, and his complaints of difficulty are evidently very sincere.
If we now turn to the origin of these remarks, it is as follows. 1822, July 12, Gruithuisen discovered in the region before us what he considered to be a colossal structure consisting of regular and obviously artificial ramparts, to which he gave the name of Schröter (subsequently transferred by B. and M., when they could not find his object, to the crater so designated in our diagram). Its extent was about 23 miles each way, but it was very dark, and situated in one of the darkest parts of the Moon, and was visible only on the terminator. Its general outline accurately faced the points of the compass, there being a central ridge from N. to S., from which branched off at an angle of 45° on either side, a number of parallel walls, like the the veins of an alder or rose-leaf, running respectively S.E. and S.W. Those running S.E. flattened gradually down : but those on the other side formed, with a second oblique rampart, lying as it would seem N.W. and S.E., enclosed spaces, which in his view would be thus sheltered from the N.N.W. polar wind. From 3 to 4 years later he and Schwabe detected external prolongations of several of these S.W. walls, that were in like manner stopped by another closing ridge. In 1826 Schwabe saw 5 fresh walls of this kind, some only of which Gr. could make out. The latter considered it remarkable that previous to the discovery of these new ramparts, a small ring was distinctly visible on their site, occasionally almost obscured by fog, of which not a trace could be subsequently perceived; and it was equally remarkable that in 1822 he always saw a small rampart completing the outline on the E., which afterwards disappeared, and beyond the E. ramparts a hill, the centre of 5 radiating ridges like a star, which have so totally vanished since, that the slight vestige of a roundish height alone remains. The regular figure itself he often found so covered with what seemed foggy clouds, that only unconnected traces of the ramparts could be seen, and the general form was lost; and such he supposed must have been the case at the time when Lohrm. drew the region before he heard of Gri's discovery. On the contrary the surrounding natural features have always remained the same; the high hill ou the N. which terminates the central wall (T, of B. and M.); the somewhat smaller hill by which the great closing rampart running from S.E. to N.W. is cut off; and the little ring (a of B. and M.) in which the straight central rampart and the closing rampart terminate—though within this ring he bad perceived many variations. Such was the curious figure which was at the time so celebrated in Germany, and which was seen by many continental observers, including Prince Metternich, who perceived it on the first news of its discovery, while “on the other hand the learned John Bull here went away empty, and behaved himself about it as his nature inclined him ;” a somewhat illnatured criticism, for which, however, there certainly was some foundation in the inattention of our observers; at the present day, it is satisfactory to feel assured that no such taunt could be with justice directed against us. This was the figure of which B. and M. could not find a trace, when they constructed their Map-though it is somewhat singular that the ridges which they have drawn on this spot are not unlike it in character--a circumstance which seems to have quite escaped them. At a later day, however, the comparative accuracy of Gr. as an observer was to be established, even on their own not very willing testimony. They state that, 1838, May 2 and 3, a long and hitherto vainly expected opportunity arrived of examining this curious region, in which, from the longitude and latitude
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given by Gr., they concluded that his fortification was to be looked for; and this time, by means of the great Berlin achromatic of 9f in. aperture, they were successful. Two principal directions of the long ridges abounding in the district were very evident, one in the meridian, another intersecting it from N.E. in an angle of 50°. In the first direction are two low, but partially steep chains, bearing several insulated summits, which connect (a) and I' at their ends; to the second belong, among others, 4 cross banks which connect these two chains by oblique lines, so as to enclose 5 longish valleys in succession, each about Im. long by 3 wide. The uniform height of the side and cross walls, and the similarity in form and size of these hollows give an aspect of regularity to this figure, which is increased when they are filled with shadow, and the dividing ridges appear as bright, straight, narrow lines. It is, however, evident that we have only a product of nature in view. Many equally regular arrangements are to be found in the Moon, of which a remarkable instance has already been described in the environs of Aristoteles, and the magnitude of any one of these valleys is sufficient to include the greatest cities of the earth. (London, however, should have been excepted.) They further remark that a 3rd meridian chain (on E.) unites itself with the second (or central one), before it reaches T', and forms a valley with it, less precipitous than the others. Their diagram shows it also connecting itself with the central chain near its middle; and gives two strong prolongations, each composed of more than one ridge, of the oblique walls towards S.W. Thus the main features of the figure are well made out; the observers however have not stated, what must undoubtedly have been the case, that their own smaller instrument would have fully sufficed for the recovery of the object in a suitable position. It only remains for us to remark what has been seen in our own country.
The earliest verification, so far as I know, was effected by Knott, 1861, Mar. 19, when the details of B. and M. were very fairly caught with a 7-in. object-glass; and they were subsequently made out even at some distance from the terminator.1862, Feb. 7, I had a good view of it with my 5-in. objectglass, with a power of 170, definition being flaring and unpleasant, but not bad. It was not very close to the terminator, which was then bisecting Timocharis (34), and grazing the E. edge of Eratosthenes (29). The central ridge connecting r and (a) was very apparent. E. of it I could distinguish little, but on the W. I was able to reckon 4 oblique walls, the first starting from , to which a 5th very short one might be added close to (a), if I was correct in thinking that the central ridge branched out right and left at its N. end, instead of running
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up to that ring. The whole agreed more with Gr.'s description than B. and M.'s figure, in the progressive shortening of the oblique walls, towards the N., so as to give fairly one-half of the design of a tapering leaf. But my remark at the time was, “the whole object looked coarse, and though curiously arranged, would never have given me the idea of an artificial production.” The following night I could still make it out as a previously known figure, and could even count up four valleys in feeble relief. The crater (a) appeared to contain another interior ring, concurrent with the larger one on its E. side. The terminator lay at this time a very little beyond the E. end of Clavius (50), and wall of Bullialdus (60), and its own diameter beyond Copernicus (30). From this it appears that it is by no means a difficult object, and may be made out under much higher illumination than Gr. would have led us to suppose : and it is worth looking for, not merely for its curious parallelism, but still more as very suitable for studying the question, which after all seems open to further enquiry, of temporary atmospheric obscuration. It is situated in a region where the effect of variations in perspective foreshortening from libration may be neglected, and since none of the principal lines run in the parallel of latitude, there is little reason to anticipate illusion from the change of the direction of illumination due to the lunar seasons. Any permanent features ought, therefore, to be always equally visible in corresponding circumstances: the direct observations of the discoverer, and the fruitless searches of L., and B. and M., who not only esamined but drew the region in detail, would lead to a suspicion that they are not so. Future study only can decide; and if it should be found that there are variations, not explicable by changes in the angles of illumination and vision, we must look further for the cause. The existence of a lunar atmosphere is denied upon arguments of much cogency; but the question cannot be considered as finally at rest; and the region before us may be found especially suited for its decision, since from its low-lying, and at the same time irregular and complicated character it may be supposed highly favourable for the exhibition of atmospheric influence. As such, its strict examination is commended to those who love to trace the footsteps of the Maker of all things in the manifold exercise of His creativo power.
TRANSITS OF JUPITER'S SATELLITES. Oct. 1st. II. egress, 7h. 26m., Ditto shadow, 9h. 8m.3rd. III. egress, 7h. 51m. Ditto shadow ingress, Th. 52m. Ditto ditto egress, 11h. 29m.—6th. I. ingress, 9h. 25m. Ditto shadow, 10h, 22m. I. egress, 1lh, 44m. Ditto shadow, 12h.
42m.-8th. I. egress, 6h. 11m. II. ingress, 6h. 56m. I. shadow egress, 7h. 10m. II. shadow ingress, Sh. 55m. II. egress, 9h. 49m. Ditto shadow, ilh. 46m.-10th. III. ingress, Th. 44m. IV. egress, 10h. 7m. III. egress, 11h. 22m. III. shadow ingress, 11h. 53m.-13th. I. ingress, 11h. 13m. Ditto shadow, 12h. 18m.—15th. I. shadow ingress, 6h. 46m. I. egress, 8h. Om. Ditto shadow, 9h. 6m. II. ingress, 9h. 22m. Ditto shadow, 11h. 34m. II. egress, 12h. 15m.--17th. III. ingress, 11h. 20m.-22nd. I. ingress, 7h. 30m. Ditto shadow, 8h. 42m. I. egress, 9h. 50m. Ditto shadow, 11h. Im. II. ingress, 11h. 50m.—26th. II. shadow egress, 6h. 22m.-27th. IV. shadow ingress, 9h. 21m.—29th. I. ingress, 9h. 22m. Ditto shadow, 10h. 37m.-31st. I. egress, Ch. 9m. Ditto shadow, 7h. 25m.
OCCULTATIONS. Oct. 15th. f Tauri, 4 mag. 7h. 38m. to 7h. 45m.—16th. 02 Tauri, 41 mag., 7h. 25m. to 8h. 9m. Q. Tauri, 4. mag. 7h. 33m. to Sh. 80 Tauri, 6 mag., 7h. 55m. to 8b. 36m. 81 Tauri, 51 mag., 8h. 6m. to 8h. 51m. 85 Tauri, 6 mag., 8h. 33m. to 9h. 27m.
A2 Tauri, 4. 10*rauri, 6 mag., 5.3 Tauri, 6 mag.
THE LUNAR ECLIPSE OF SEPTEMBER 13.
BY JOHN BROWNING, F.R.A.S.
During this eclipse several facts were noted that, carefully considered, may, I think, tend to elucidate the interesting problem of the condition or constitution of the Moon's surface. Few questions are more interesting to astronomers, and few seem more difficult of solution.
It is because of their indirect bearing upon this question that I think the points I am about to describe merit particular attention. On the 13th of September the sky during the day was overcast, and it remained thick until shortly before nine o'clock. Then, quite suddenly, it became exceedingly clear, and remained so for the greater part of the night. After the very unfavourable weather astronomers have lately had to contend with, and the tantalizing obscurity which prevailed on the night of the disappearance of the whole of Jupiter's satellites, except in large telescopes, the effect of this almost unlooked-for clearness was most cheering. This exceeding clearness probably materially modified the results that were afterwards obtained.
According to calculation, the eclipse must have commenced