Зображення сторінки

worms, confirmed by Lyonnet, Réaumur, Dugés, etc., were timidly questioned by Vandelius, and by Bosc, and more recently and positively by Williams, Vogt, and others. We must, therefore, be thankful to those who called attention to early observations, like Baird, or made fresh experiments, like Quatrefages.

The restoration of mutilated parts of Annelids is incontestible. Many of them can reproduce even the anterior region with the head. Amongst recent authors, M. de Quatrefages has demonstrated this fact over again in Eunice, and Dalyell followed step by step the reproduction of the head and branchiæ by the posterior extremity of a Sabella. I have also met several times with marine worms (Eteone, Nepthys, etc.) which have undoubtedly reproduced their anterior region, the restored portions being distinguished by lighter colour and smaller diameter. The aspect of these worms resembles that of the Heteronereids; so great is the difference in the two regions, one would think they were two portions of different worms stuck together. One interesting remark occurs with reference to this subject : If a worm is severed transversely, does the posterior part always reproduce exactly the number of segments in the suppressed anterior portion? It is probable. At least I met with an Eteone which reproduced an anterior portion of nearly fifty segments. The head is undoubtedly the first to be formed, and then fresh segments are successively produced at the junction of the old part and the new. This, however, requires to be supported by positive observations.

Geographical Distribution of Annelids.-In this section M. Claparède disputes the accuracy of M. Quatrefages in limiting the locality of species. M. Quatrefages does not admit, for example, that the Mediterranean and the ocean can be inhabited by the same species, and sometimes makes specific distinctions out of the fact of locality only. He also maintains that littoral species cannot live under such changes as the presence or absence of tides. At Naples, however, M. Claparède kept littoral Annelids for months in captivity, and found the best mode of making them prosper was to deprive them of water for some hours each day, in order that the vessel might be oxygenated.

Classification. On this subject M. Claparède remarks that we are approaching a natural classification, and that the families now established are for the most part well founded. He does not propose any new families.






Much of the story of Copernicus remained untold when we broke off last month, and what we have already heard may well give us an interest in the remainder. It will be matter of familiar observation how striking is its aspect under very varied angles of illumination-how the magnificence of its broad and massive wall, and the extraordinary roughness of its glacis, as it rises upon the terminator, give place to a relief in higher sunlight which exhibits the serpentine terraces, the central elevations, and the whole arrangement of the structure in a more intelligible manner; and how this aspect is again gradually replaced under increased illumination by one of more delicate but still very expressive relief, and of considerable permanency; I have seen a little true shadow cast from the great peak in the W. wall, and from a steep terrace on that side, as late as 3d. 1. h. before Full Moon. The beauty of these very dissimilar, yet intimately related aspects must be seen, and studied, to be fully appreciated. Mention ought to be made of a very striking engraving proceeding from the Collegio Romano,* as exhibiting the latter of these positions on a large scale, and with much cleverness of effect as well as fullness of detail, but, we are obliged to add, some degree of inattention also. We shall, however, proceed at present with an abstract of the remarks of B. and M. on its immediate vicinity. It is enclosed by a great mass of closely crowded mountain chains, arranged in lines partly radiating, partly parallel to the ring, especially on E. Here many of them are of very slight elevation (250 to 650 ft.), but on the opposite side they reach nearly 3000 ft. Craters are first found at some distance, and but few in the mountains themselves, though those very obvious ;" a great contrast, by the way, to the aspect of many other large cavities and their rings, as though the eruptive action had here more completely exhausted itself at one wide and unimpeded aperture. One is a small twin-crater (Copernicus A) on the S. slope, already seen by Schr., the larger orifice lying N., so deep that it holds its shadow longer than the great crater itself; its ring, of 6° light, is much more distinct from its interior of 3° than is usual in such little cavities; the small crater B, equidistant from the grand ring S.E., appears of similar depth. Towards the foot of the N.E. glacis, à larger opening, Gay Lussac, has broken through; this with its smaller companion, 4800 ft. deep according to Schr., was discovered by him, as well as a curious cleft running E.S.E. from it for some distance, which he compared to the great valley in the Alps, from the way in which its sloping sides are studded with small irregular hills, as though an upheaved and hollow ridge had fallen in, leaving the firmer portions hanging on its declivities. In the Roman drawing, the end next the crater is feathered out into oblique lateral fissures.

* Memoirs Roy. Astron. Society, XXXII. pl. viii.

But the more remarkable features here are the great lightstreaks which diverge from it in every direction. They form a less regular system of radiation than is to be found issuing from other centres, but still their relation to Copernicus as a departure point cannot be mistaken. Several of them connect this great crater with others in the neighbourhood which repeat the phænomenon, though on a smaller scale; in fact, but few large rings between the equator and 30° N. Lat. are wholly without them, and some exhibit them even beyond that limit. Near Copernicus they are merged in a bright but confused “nimbus,” or glory, interrupted here and there by streaks and insulated patches of darkness, of which one is even found close to the wall. Further out they expand, and direct themselves partly in divergent, partly in parallel lines, to the neighbouring craters. Those pointing S. towards Reinhold (31) and Gambart (a crater between Reinhold and Sömmering-Int. Obs., xii. 218) are more feeble and ill-defined; they seem to indicate a fresh focus at Reinhold, but do not diverge from it again : those directed towards Schröter are more considerable, but do not reach the hill country; and here the aspect of the surface is rather that of dark streaks traversing brightness than the reverse. One such large dark streak passes from Copernicus A to Stadius, the S. quarter of which it includes, and then is lost. The darkest of these begin at a grey mountain marked &, and extend S.W. for 40 miles : the inquiry of B. and M. whether one or other of the unascertained spots of Riccioli is to be recognized here, must appear singular after a slight comparison of the old maps, which leave no doubt of identification as to his Rhoticus, though some regret at its not having been more accurately delineated in their great map. Towards Eratosthenes almost all the light is united in one mass, of which the brightness of the Sinus stuum may be considered a continuation. Further N. begin some very prominent streaks, few less than five miles broad, one leading to Lambert (35), 14 miles; some, which seem to start in the plain itself, are crossed obliquely by others coming from Eratosthenes the reverse way.

Towards N. they are narrower and much interrupted; they are larger and more intense N.E. A great divided streak passes from Mayer (32)--a large crater N.E. of Copernicus, with a smaller one on its W. edge-to Euler (36); others pass through the Oceanus Procellarum to meet the narrow and not easily distinguishable streaks of Aristarchus (43), and run into a great spot of light between both. Others, shorter and less distinct in appearance and direction, are found S. of Mayer. On the side of Kepler (41) they are more clear and decided : several, nearly parallel, run E. to that crater, and enter its “nimbus,” thus uniting the two main streaksystems of the N. hemisphere. These details are so far worthy of record, as the suspicion of change in the reflective power of portions of the lunar surface, if not yet warranted, is not unreasonable. The streaks are of course best seen in Full Moon, very little of them being visible if the terminator has not passed Mayer in the increase, or reached Eratosthenes in the wane, and that little being masked by the opposite direction of the mountain ridges.

Copernicus and its nimbus can be clearly made out on the night-side before the First, not so readily after the last Quarter.

We now come to a very singular region, more than once adverted to in our previous paper, and certainly in its own way one of the most remarkable in the Moon;- the Craterchains, as we may term them, between Copernicus and Eratosthenes. Here we find the greatest and strangest contrast to the neighbouring Sinus Æstuum. There, craters are all but invisible, even after the strictest search: here they exist in such profusion that it is doubtful whether any really level surface intervenes. The sixty-one shown in the map, of which the greater part lie in a line between Pytheas (a moderatesized crater two-thirds of the way from Copernicus to Lambert) and Stadius, are probably not the half that are perceptible, but past delineation. They are not scattered at random through the plain, but lie behind one another in rows, in some places closely compressed, in others wider apart at nearly equal distances, and but few seem entirely insulated. Though the majority are very minute, and only a few exceed 1" in diameter, B. and M. cannot give them, like Gruithuisen, a width of only 500 (French) feet, but would estimate most of them at as many toises (3200 feet). The closely compressed rows, they observe, assume easily the aspect of a connected cleft; and, in fact, the two forms are nearly interchangeable; we only need imagine the absence of a common and usually very low partition, to convert the one into the other. At the N. end of the landscape, for the length of a lunar degree, there is such a cleft, with a distinct embankment on either side, and four of the smallest craters in its depth, with which the next three craters S. of it often seem to form a whole. At a distance of 20° at furthest from the terminator this crater-swarm becomes invisible, and the surface is then almost exactly similar in aspect to the Sinus Æstuum itself.

The discovery of this very singular region is due to Gruithuisen, 1815. He has well described its aspect, and speaks of the rows of craters as forming in places hollow ways, or being connected by a large longitudinal furrow, while the separate craters had outlets E. and W., which, however, are not visible if the illumination is precisely in that direction. And then he goes on, in his own way, to refer to the especial fertility indicated by the darkness of the soil; and considers them, if not volcanos, the artificial dwellings of living beings; in another place indicating his own choice between the alternatives by asserting that there is not a trace of a volcano, ancient or modern, upon the Moon! all its cavities having been formed by the impact of masses falling from space-of which portions still protrude as central hills ! They are mentioned again by Kunowsky, 1821, who says that he often distinctly recognized, in clefts, rows of crater-like eruptions. Lohrmann's Sections and letterpress unfortunately do not include this region : his General Map indicates broad, low ridges, pierced with a moderate number of craters ; but, though the first impression is not that of similarity to the Map of B. & M., a closer inspection shows that the objects represented must have been nearly

A corresponding view with that of Kunowsky is taken by Schmidt, who remarks that “everywhere a keen and unprejudiced course of observation will indicate that rills (clefts) are only crater-rows in a particular modification, as the innumerable transition-forms prove, and as Mädler first (?) pointed out.” Little craters, he tells us, often lie in long lines, as if they had broken out of a crack, and he enumerates about 300 visible in the region now under discussion, many of which are contiguous, and frequently so confluent as to form ravines like regular clefts : their external height being, he thinks, very insignificant-somewhere between 150 and 600 feet.

Why these crater-chains were unnoticed by Schr. is a question which, though it seems to have been never asked, is deserving of an attempt at a reply. It so happens, indeed, that Eratosthenes and Copernicus were examined by him at different times, and represented in separate views; and that these miniature volcanos soon disappear after sunrise ; and it may be admitted that he overlooked many small objects in various places. But, on the other hand, it must be borne in mind that his attention was evidently frequently directed to Copernicus ; that the object, though fugitive, is in a very remarkable and conspicuous place, and is by no means collect

the same.

« НазадПродовжити »