dropping vertically upon the ancient shore and obliterating it, while
its giant neighbor, Le Monnier, opens a yawning mouth as if to swallow
the sea itself. A scene like this makes one question whether, after
all, those may not be right who have imagined that the so-called sea
bottoms are really vast plains of frozen lava which gushed up in
floods so extensive that even the mighty volcanoes were half drowned
in the fiery sea. This suggestion becomes even stronger when we turn
to another of the photographs of Mr Ritchey's wonderful series,
showing a part of the Mare Tranquilitatis (``Sea of Tranquility''!).
Notice how near the center of the picture the outline of a huge ring
with radiating ridges shows through the sea bottom; a fossil volcano
submerged in a petrified ocean! This is by no means the only instance
in which a buried world shows itself under the great lunar plains.
Yet, as the newer craters in the sea itself prove, the volcanic
activity survived this other catastrophe, or broke out again
subsequently, bringing more ruin to pile upon ruin.

Yet notwithstanding the evidence which we have just been considering
in support of the hypothesis that the ``seas'' are lava floods,
Messrs. Loewy and Puiseux, the selenographers of the Paris
Observatory, are convinced that these great plains bear characteristic
marks of the former presence of immense bodies of water. In that case
we should be forced to conclude that the later oceans of the moon lay
upon vast sheets of solidified lava; and thus the catastrophe of the
lunar world assumes a double aspect, the earliest oceans being
swallowed up in molten floods issuing from the interior, while the
lands were reduced to chaos by a universal eruption of tremendous
volcanoes; and then a period of comparative quiet followed, during
which new seas were formed, and new life perhaps began to flourish in
the lunar world, only to end in another cataclysm, which finally put a