several crater rings, only a third, a
quarter, or a fifth as great in diameter, have broken forth, and these
in turn have been partially destroyed, while in the interior of the
oldest of them yet smaller craters, a nest of them, mere Etnas,
Cotopaxis, and Kilaueas in magnitude, simple pinheads on the moon, have
opened their tiny jaws in weak and ineffective expression of the waning
energies of a still later epoch, which followed the truly heroic age of
lunar vulcanicity.

This is only one example among hundreds, scattered all over the moon,
which show how the surface of our satellite has suffered upheaval after
upheaval. It is possible that some of the small craters, not included
within the walls of the greater ones, may represent an early stage in
the era of volcanic activity that wrecked the moon, but where larger and
smaller are grouped together a certain progression can be seen, tending
finally to extinction. The internal energies reached a maximum and then
fell off in strength until they died out completely.

It can hardly be supposed that the life-bearing phase of lunar
history--if there ever was one--could survive the outbreak of the
volcanic cataclysm. North America, or Europe, if subjected to such an
experience as the continental areas of the moon have passed through,
would be, in proportion, worse wrecked than the most fearfully battered
steel victim of a modern sea fight, and one can readily understand that,
in such circumstances, those now beautiful and populous continents would
exhibit, from a distance, scarcely any token of their present
topographical features, to say nothing of any relics of their occupation
by living creatures.

There are other interesting glimpses to be had of an older world in the
moon than that whose scarred face is now beautified for us by distance.
Not far from Theophilus and the other great crater-mountains just
described, at the upper, or southern, end of the level expanse called
the "Sea of Nectar," is a broad, semicircular bay whose shores are
formed by the walls of a partially destroyed crater named Fracastorius.
It is evident that this bay, and the larger part of the "Sea of Nectar,"
have been created by an outwelling of liquid lavas, which formed a
smooth floor over a portion of the pre-existing surface of the moon, and
broke down and submerged a large part of the mountain ring of
Fracastorius, leaving the more ancient walls standing at the southern
end, while, outlined by