hich generally radiate in long
rows from the outer foot of the slope. The spurs usually abut on the
wall, and, either spreading out like the sticks of a fan or running
roughly parallel to each other, extend for long distances, gradually
diminishing in height and width till they die out on the surrounding
surface. They have been compared to lava streams, which those round
Aristillus, Aristoteles, and on the flank of Clavius _a_, certainly
somewhat resemble, though, in the two former instances, they are rather
comparable to immense ridges. In addition to the above, the spurs
radiating from the south-eastern rampart of Condamine and the long
undulating ridges and rows of hillocks running from Cyrillus over the
eastern _glacis_ of Theophilus, may be named as very interesting
examples.

Neison and some other selenographers place in a distinct class certain of
the smaller ring-plains which usually have a steeper outer slope, and are
supposed to present clearer indications of a volcanic origin than the
ring-plains, terming them "Crater-plains."

CRATERS.--Under this generic name is placed a vast number of formations
exhibiting a great difference in size and outward characteristics, though
generally (under moderate magnification) of a circular or sub-circular
shape. Their diameter varies from 15 miles or more to 3, and even less,
and their flanks rise much more steeply to the summit, which is seldom
very lofty, than those of the ring-plains, and fall more gradually to the
floor. There is no portion of the moon in which they do not abound,
whether it be on the ramparts, floors, and outer slopes of walled and
ring plains, the summits and escarpments of mountain ranges, amid the
intricacies of the highlands, or on the grey surface of the Maria. In
many instances they have a brighter and newer aspect than the larger
formations, often being the most brilliant points on their walls, when
they are found in this position. Very frequently too they are not only
very bright themselves, but stand on bright areas, whose borders are
generally concentric with them, which shine with a glistening lustre, and
form a kind of halo of light around them. Euclides and Bessarion A, and
the craters east of Landsberg, are especially interesting examples. It
seems not improbable that these areas may represent deposits formed by
some kind of matter ejected from the craters, but whether of ancient or
modern date, it is, of course, impossible to determine.