The assumed First Meridian passes the middle of the illuminated disk at

Major and minor semi-axes of the apparent orbits of the satellites, expressed in semi-diameters of Saturn's equator.

Mimas. Encel. Tethys. Dione. Rhea. Titan. Iapetus

The centre of the apparent ellipse described by Titan may be assumed to be o'60 semi-diam. east of the centre of the ball. The posit.-angles of its axes are o°56, and those of the orbit of Iapetus on Oct. 2, 12°35, and on Nov. 1, 12°17 less than the pos. angles of those of the inner satellites.

Approximate Greenwich times of some of the conjunctions of the satellites with the ends of the ring, and also of some of their greatest elongations.-V. p. 189:

Careful observations of the conjunctions of Titan and of its distance from the major axis of the ring on Sept. 30, Oct. 8, 16, 24, Nov. I are most desirable. Iapetus reaches its inferior conjunction on Oct. 11, and its greatest western elongation on Oct. 31.

A. M.

Books Received.-De l'origine et de l'établissement des mouvements astronomiques. Par M. C. Lagrange. Bruxelles : F. Hayez. 1878.— Description of Observatory at Higher Bebbington, Cheshire. By R. C. Johnson.-The Stars in their Courses. By T. S. Bazley. London: Trübner & Co. 1878.-Micrometrical Measurements of 517 Double Stars at Cincinnati Observatory. O. Stone, Director. Cincinnati : Peter Thornham. 1878.

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(Translated from Sirius, 1878, p. 79.)

In the central and best seen portion of the disk of the moon, between the crater Hyginus and the walled plain Boscovich, there is a dark district, flat towards the east, but in the west intersected by a series of parallel chains of hills, which at the full moon are remarkable for their unusually dark colour. This region is bounded eastwards by the great furrow of Hyginus, at the west bank of which there is a curiously curved mountain, or rather system of hills which, as Mädler very characteristically describes it, presents the appearance of a spiral arrangement. The first person to make a drawing of this neighbourhood was Schröter, who has, speaking generally, indicated correctly the position of the western grey chains of hills, as also the course of the large Hyginus furrow. At the position of the Spiral Mountain his drawing represents a sickle-shaped range of hills together with a crater, whereby one perceives that he saw the mountain imperfectly. Lohrmann gave a more accurate representation of the entire district on the first sheet of his map of the moon; Mädler, however, a few years afterwards gave a still better one, inasmuch as he published a special map of the neighbourhood of Hyginus on a scale twice and a half as large as that of his great lunar map. This special map represents the district in question very correctly, speaking in a general way, and contains a vast number of small craters and low ridges of hills which had

VOL. XVI.

escaped earlier observers. The great lunar map of Schmidt, in Athens, agrees admirably with Mädler's special drawing, and in the level district westward of Hyginus contains in its turn a few additional craters, which are, however, the minima of visibility, and to be made out only when near the terminator in very fine instruments. The district of the moon's surface here spoken of, which at every lunation is to be observed with equal distinctness at the time of the first or last quarter, has consequently been as thoroughly investigated and sketched as it is well possible to imagine, and it can admit of no doubt that should a crater larger and more distinct than the other ones make its appearance here, it may be inferred, with a certitude that cannot be surpassed, that we have to do with a recent formation.

Now this is the case that has occurred. For nearly eleven years I have occupied myself specially with observations of the moon, and in doing so have on numberless occasions viewed the neighbourhood round about Hyginus without noticing objects that were in variance with the recognized maps. On the 19th of May, 1877, I examined, after a shower of rain, the flat region to the west of Hyginus, employing powers of 135, 200, and 300, and at once caught sight here of a large black crater filled with shadow, without any wall, which, from my intimate acquaintance with this district, I at once recognized as one that I had never seen as yet. The moon was not as clear as it usually is, and of the small craters in the grey plain there was but one that was visible, to the south of the new one, and considerably smaller than that was. Unfavourable weather prevented a continuance of the observations, but on the 18th of July an opportunity of examining the new crater was again offered. The air was not very good, the moon, going down and boiling. I was nevertheless able to see distinctly the small craters in the plain to the west of Hyginus, and the shadows of their walls could indeed he made out. The new crater was seen as a large black spot surrounded by a vapourous border. Only in favourable moments was a sharply circumscribed nucleus to be recognized as distinguished from the undefined border. The whole, to a person who had been long familiar with the objects seen in the moon, presented an excessively mysterious appearance, from being much darker than the dark spot indicated by Mädler at a certain distance towards the west. Later on I imagined I made out, in addition, a small, hazy, circular spot which was not visible at the commencement of the observation. On the following day, the 19th of June, the small craters in the plain were seen distinctly and without difficulty, whereas the new, large crater had disappeared. At the place it had occupied there was perhaps seen an undefined