ight on their sites
and their apparent prolongations. He observed it in the ring-plain
Eudoxus, crossing the southern side of the floor from wall to wall; and
also in connection with the prominent cleft running from the north side
of Burg to the west of Alexander, and in some other situations. He terms
these phenomena _Murs enigmatiques_. Apparent prolongations of clefts in
the form of rows of hillocks or small mounds are very common.

FAULTS.--These sudden drops in the surface, representing local
dislocations, are far from unusual: the best examples being the straight
wall, or "railroad," west of Birt; that which strikes obliquely across
Plato; another which traverses Phocylides; and a fourth that has
manifestly modified the mountain arm north of Cichus. They differ from
the terrestrial phenomena so designated in the fact that the surface
indications of these are destroyed by denudation or masked by deposits of
subsequent date. In many cases on the moon, though its course cannot be
traced in its entirety by its shadow, yet the existence of a fault may be
inferred by the displacement and fracture of neighbouring objects.

VALLEYS.--Features thus designated, differing greatly both in size and
character, are met with in almost every part of the surface, except on
the grey plains. While the smallest examples, from their delicacy,
tenuity, and superficial resemblance to rills, are termed rill-valleys,
the larger and more conspicuous assume the appearance of coarse chasms,
gorges, or trough-like depressions. Between these two extremes, are many
objects of moderate dimensions--winding or straight ravines and defiles
bounded by steep mountains, and shallow dales flanked by low rounded
heights. The rill valleys are very numerous, only differing in many
instances from the true rills in size, and are probably due to the same
cause. Among the most noteworthy valleys of the largest class must, of
course, be placed the great valley of the Alps, one of the most striking
objects in the northern hemisphere, which also includes the great valley
south-east of Ukert. The Rheita valley, the very similar chasm west of
Reichenbach, and the gorge west of Herschel, are also notable examples in
the southern hemisphere. The borders of some of the Maria (especially
that of the Mare Crisium) and of many of the depressed rimless
formations, furnish instances of winding valleys intersecting their
borders: the hilly regions likewise often abound in l