more difficult.  A few miles E. of Ariadaeus it sends out a short branch, running in a S.W. direction, which can be traced as a fine white line under a moderately high sun.  It is interesting to follow the course of the principal cleft across the plain, and to note its progress through the ridges and mountain groups it encounters.  In the great Lick telescope it is seen to traverse some old crater-rings which have not been revealed in smaller instruments.  About midway between Ariadaeus and Silberschlag it exhibits a duplication for a short distance, first detected by Webb.

DE MORGAN.—­A brilliant little crater, 4 miles in diameter, on the plain S. of the Ariadaeus cleft.

CAYLEY.—­A very deep bright crater, with a dark interior, N. of the last, and more than double its diameter.  There is a second crater between this and the cleft.

WHEWELL.—­Another bright little ring, about 3 miles in diameter, some distance to the E. of De Morgan and Cayley.

SOSIGENES.—­A small circular ring-plain, 14 miles in diameter, with narrow walls, a central mountain, and a minute crater outside the wall on the E.; situated on the E. side of the Mare Tranquilitatis, W. of Julius Caesar.  There is another crater, about half its diameter, on the S., connected with it by a low mound.  This has a still smaller crater on the W. of it.

JULIUS CAESAR.—­A large incomplete formation of irregular shape.  The wall on the E. is much terraced, and forms a flat “S” curve.  The summit ridge is especially bright, and has a conspicuous little crater upon it.  On the W. is a number of narrow longitudinal valleys trending from N. to S., included by a wide valley which constitutes the boundary on this side.  The border on the S. consists of a number of low rounded banks, those immediately E. of Sosigenes being traversed by several shallow valleys, which look as if they had been shaped by alluvial action.  There is a brilliant little hill at the end of one of these valleys, a few miles E. of Sosigenes.  The floor of Julius Caesar is uneven in tone, becoming gradually duskier from S. to N., the northern end ranking among the darkest areas on the lunar surface.  There are at least three large circular swellings in the interior.  A long low mound, with two or three depressions upon it, bounds the wide valley on the E. side.

GODIN.—­A square-shaped ring-plain, 28 miles in diameter, with rounded corners.  The bright rampart is everywhere lofty, except on the S., is much terraced, and includes a central mountain.  On the S. a curious trumpet-shaped valley, extending some distance towards the S.W., and bounded by bright walls, is a noteworthy feature at sunrise.  There are other longitudinal valleys with associated ridges on this side of the formation, all running in the same direction.  There is a large bright crater outside the border on the N.E., and, between it and the wall, another, smaller, which is readily seen under a high sun.