forth from orifices or rents communicating with the interior, and
overspread and partially filled up these immense hollows, more or less
overwhelming and destroying many formations which stood upon them before
this catastrophe took place. Though this, like many other speculations of
a similar character relating to lunar "geology," must remain, at least
for the present, as a mere hypothesis; indications of this partial
destruction by some agency or other is almost everywhere apparent in
those formations which border the so-called seas, as, for example,
Fracastorius in the Mare Nectaris; Le Monnier in the Mare Serenitatis;
Pitatus and Hesiodus, on the south side of the Mare Nubium; Doppelmayer
in the Mare Humorum, and in many other situations; while no observer can
fail to notice innumerable instances of more or less complete
obliteration and ruin among objects within these areas, in the form of
obscure rings (mere scars on the surface), dusky craters, circular
arrangements of isolated hills, reminding one of the monoliths of a
Druidical temple; all of which we are justified in concluding were at one
time formations of a normal type. It has been held by some selenologists
--and Schmidt appears to be of the number,--that, seeing the comparative
scarcity of large ring-plains and other massive formations on the Maria,
these grey plains represent, as it were, a picture of the primitive
surface of the moon before it was disturbed by the operations of interior
forces; but this view affords no explanation of the undoubted existence
of the relics of an earlier lunar world beneath their smooth superficies.

MARIA.--Leaving, however, these considerations for a more particular
description of the Maria, it is clearly impossible, in referring to their
level relatively to the higher and brighter land surface of the moon, to
appeal to any hypsometrical standard. All that is known in this respect
is, that they are invariably lower than the latter, and that some sink to
a greater depth than others, or, in other words, that they do not all