and can be traced up to the N. border, but not farther.  Schmidt represents the first as a crater-row, which it probably is, as it varies considerably in width.  From the S.E. side of the formation extends a long cleft, terminating at the end of a prominent spur from the S. side of the Carpathians.  There are also two remarkable rill-like valleys, commencing on the N. of Gay-Lussac A, which curve round the W. side of Gay-Lussac.

HORTENSIUS.—­This brilliant crater, about 10 miles in diameter, is remarkable for its depth, and as being a ray-centre surrounded by a nimbus of light.  It has a central mountain, and Schmidt shows a minute crater on the outer slope of the S. wall.  The former is a test object.

MILICHIUS.—­Is situated on the N.N.E. of Hortensius.  It is fully as bright, but rather smaller.  Its floor, apparently devoid of detail, is considerably depressed below the surrounding surface.

TOBIAS MAYER.—­Like Gay-Lussac, a noteworthy ring-plain associated with the Carpathian Mountains.  It is 22 miles in diameter, and has a wall which rises on the W. to a height of nearly 10,000 feet above the floor; on the latter there is a conspicuous central mountain, and on the E. side a crater, and some little hills.  Schmidt shows a smaller crater on the W. side, which I have not seen.  Adjoining the formation on the W. is a ring-plain of about one-fourth its area, which is a bright object.  Tobias Mayer and the neighbouring Carpathians form an especially beautiful telescopic picture at sunrise.

KUNOWSKY.—­An inconspicuous ring-plain, about 11 miles in diameter, standing in a barren region in the Mare Procellarum, W.S.W. of Encke.  The central mountain is tolerably distinct.

ENCKE.—­A regular ring-plain, 20 miles in diameter, with a comparatively low border, nowhere rising more than 1800 feet above the interior, which is depressed some 1000 feet below the surrounding Oceanus Procellarum.  A lofty ridge traverses the floor from S. to N., bifurcating before it reaches the N. wall.  There is a bright crater on the W. wall, and a depression on the opposite wall, neither of which, strange to say, is shown on the maps.  Encke is encircled by ridges, which, when it is on the morning terminator, combine to make it resemble a large crater surrounded by a vast mountain ring.

KEPLER.—­One of the most brilliant objects in the second quadrant,—­a ring-plain about 22 miles in diameter, with a lofty border; a peak on the E. attaining an altitude of 10,000 feet above the surface.  The wall is much terraced, especially the outer slope on the W., where a narrow valley is easily traceable.  Though omitted from the maps, there is a prominent circular depression on the W. border, which forms a distinct notch thereon at sunrise.  On the N., the wall exhibits a conspicuous gap.  There is a central hill on the floor.  Immediately E. of Kepler is a bright plateau, bounded on the N. by a very straight border, with two small craters on its edge.  Both these objects are incomplete on the N., as if they had been deformed by a “fault,” which has apparently affected the N. end of Kepler also.  Kepler is the centre of one of the most extended systems of bright streaks on the moon’s visible surface.