and south-western sides.

This range gradually sinks in the

east, and a beautiful sloping beach seems to extend down to the level surface of the inclosed lake (as we shall call it, for want of other language). With the highest telescopic power, under the most favourable circumstances, I never could detect the slightest irregularity in the shading of the surface of the lake. Had the cavity been filled with quicksilver, and suddenly congealed or covered with solid ice, with a covering of pure snow, the shading could not be more regular than it is. To add, however, to the terrene likeness, into this seeming lake there flows what looks exactly as a river should at such a distance. That there is an indentation in the surface, exactly like the bed of a river, extending into the country (with numerous islands), for more than a hundred miles, and then forking and separating into two distinct branches, each of which pursues a serpentine course for from thirty to fifty miles beyond the fork,—all this is distinctly visible. I may say, indeed, that, just before entering the lunar lake, this lunar river is found to disappear from sight, and seems to pass beneath the range of hills which border the lake. The region of country which lies between the forks or branches of this seeming river is evidently higher, and to the eye appears just as it should do, so as to shed its water into the stream which appears to flow in the valley below. The question may be asked, Why is this not a lake and a river? There is no lunar atmosphere on the visible hemisphere of the moon, such as surrounds the earth; and if there were water like ours on the moon, it would be soon evaporated, and would produce a kind of vaporous atmosphere, which ought to be shown in some of the many phenomena involving the moon, but which has not yet been detected. What, then, shall we call the objects described? I can only answer that this phenomenon, with many other, presented by the lunar surface, has thus far baffled the most diligent and persevering efforts to explain. In some of these cavities, where the tinting of the level surface is perfect with an ordinary telescope, when examined

with instruments of the highest power, we detect small depressions in this very surface, cup-shaped, and in all respects resembling the form and features of the principal cavity. These hollow places are clearly marked by the shadows cast on the interior of the edges, which change as the sun changes, and seem to demonstrate that these level surfaces do not belong to a fluid but to a solid substance.

Among what are called the volcanic mountains of the moon, are found objects of special interest. One of them, named Copernicus, and situated not far from the moon's equator, is so distinctly shown by the telescope, that the external surface of the surrounding mountains presents the very appearance we should expect to find in mountains formed by the ejecting from the crater of immense quantities of lava and melted matter, solidifying as it poured down the mountain-side, and marking the entire external surface with short ridges and deep gullies, all radiating from a common centre. Can these be, indeed, the overflowing of once active volcanoes? Sir William Herschel once entertained the opinion that they were; and, with his great reflecting telescope, at one time discovered what he believed to be the flames of an active volcano on the dark part of the new moon. More powerful instruments have not confirmed this discovery; and although a like appearance of a sort of luminous or brilliant spot has been seen by more than one person, it is almost impossible to assert the luminosity to be due to a volcano in a state of irruption; but it is more commonly supposed to be some highly reflective surface of short extent, and for a time favourably situated to throw back to us the earth-shine of our own planet.

From some of these seeming volcanoes there are streaky radiations or bright lines, running from a common centre, and extending sometimes to great distances. These have by some been considered to be hardened lava-streams of great reflective power; but, unfortunately for this hypothesis, they hold their way unbroken across deep valleys and abrupt depressions, which no molten matter flowing as lava

does, could possibly do. To me they more resemble immense upheavals, forming elevated ridges of a reflecting power greater than that of the surrounding country.

We find on the level surfaces a few very direct cuts, as they may be called, not unlike those made on our planet for railway-tracks, only on a gigantic scale, being more than a thousand yards in width, and extending in some instances over a hundred miles in length. What these may be it is useless to conjecture. We cannot regard them as the work of sentient beings, and must rather consider them as abrupt depressions or faults in the lunar geography.

THE MOON'S CENTRE OF FIGURE.-The wonderful phenomena presented to the eye on the visible hemisphere of the moon have been rendered in some degree explicable by a remarkable discovery recently made, that the centre of gravity of the moon does not coincide with the centre of figure. This is not the place to explain how this fact has been ascertained. It is now introduced to present its effect on the hither portion of the lunar orb.

If the material composing the moon was lighter in one hemisphere than in the other, it is manifest that the centre of gravity would fall in the heavier half of the globe. For instance, a globe composed partly of lead and partly of wood could not have the centre of gravity coincident with the centre of the globe; but it would lie somewhere in the leaden hemisphere. So it now appears that the centre of gravity of the moon is more than thirty-three miles from the centre of figure, and that this centre of gravity falls in the remote hemisphere, which can never be seen by mortal eye.

Now, the centre of gravity is the centre to which all heavy bodies gravitate. About it as a centre the lunar ocean and the lunar atmosphere, in case such exist, would arrange themselves, and the lighter hemisphere would rise above the general level, as referred to the centre of gravity to an extreme height of thirty-three miles. Admitting this to be true, and as we shall see hereafter the fact appears to be well established, we can readily perceive that no water

river, lake, or sea, should exist on the hither side of the moon, and no perceptible atmosphere can exist at so great an elevation. Even vegetable life itself could not be maintained on a mountain towering up to the enormous height of thirty-three miles; and hence we ought to expect the hither side of our satellite to present exactly such an appearance rs is revealed by telescopic inspection.

If the centres of gravity and figure ever coincided in the moon, and the change of form has been produced by some great convulsion, which has principally expended its force in an upheaval of the hither side of the globe, then we can account for the rough, broken, and shattered condition of the visible surface. Lakes and rivers may once have existed, active volcanoes might once have poured forth their lavastreams, while now the dry and desolate beds and the extinct craters are only to be seen.

The consequences which flow from this singular discovery, as to the figure of our satellite, are certainly very remarkable, and will doubtless be traced with deep interest in future examinations.

OCCULTATIONS.-As the moon is very near the earth, and her disc covers a very considerable surface in the heavens in her sweep among the fixed stars, she must of course cross over a multitude of stars in her revolutions. A star thus hidden by the moon is said to be occulted, and these occultations are phenomena of special interest on many accounts. As a general thing, star even of the first magnitude, in passing under the dark limb of the moon, vanishes from the sight instantaneously, as though it were suddenly stricken from existence, and at its re-appearance its full brilliancy bursts at once on the eye. This demonstrates the fact that the stars can be nothing more than luminous points to our senses, even when grasped by the greatest telescopic power.

A strange appearance sometimes attends the occultation stars by the moon. The star comes up to the moon's , entirely vanishes for a moment, then re-appears, glides