Future observers
will perhaps be in a better position to decide the question without
cavil, if such eruptions should again take place. Like the larger
enclosures, these smaller objects frequently encroach upon each other--
crater-ring overlapping crater-ring, as in the case of Thebit, where a
large crater, which has interfered with the continuity of the east wall,
has, in its turn, been disturbed by a smaller crater on its own east
wall. The craters in many cases, possibly in the majority if we could
detect them, have central mountains, some of them being excellent tests
for telescopic definition--as, for example, the central peaks of
Hortensius, Bessarion, and that of the small crater just mentioned on the
east wall of Thebit A. A tendency to a linear arrangement is often
displayed, especially among the smaller class, as is also their
occurrence in pairs.

CRATER-CONES.--These objects, plentifully distributed on the lunar
surface, are especially interesting from their outward resemblance to the
parasitic cones found on the flanks of terrestrial volcanoes (Etna, for
instance). In the larger examples it is occasionally possible to see that
the interiors are either inverted cones without a floor, or cup-shaped
depressions on the summit of the object. Frequently, however, they are so
small that the orifice can only be detected under oblique illumination.
Under a high sun they generally appear as white spots, more or less ill-
defined, as on the floors of Archimedes, Fracastorius, Plato, and many
other formations, which include a great number, all of which are probably
crater cones, although only a few have been seen as such. It is a
significant fact that in these situations they are always found to be
closely associated with the light streaks which traverse the interior of
the formations, standing either on their surface or close to their edges.
The instrumental and meteorological requirements necessary for a
successful scrutiny of the smallest type of these features, are beyond
the reach of the ordinary observer in this country, as they demand direct
observation in large telescopes under the best atmospheric conditions.

Some years ago Dr. Klein of Cologne called attention to some very
interesting types of crater-cones, which may be found on certain dark or
smoky-grey areas on the moon. These, he considers, may probably represent
active volcanic vents, and urges that they should be diligently examined
and watched by obs