as well perhaps as a thin layer of the planet's original surface; so
that when in due course the whole of the meteor-swarm had been captured,
Mars had acquired its present mass, but would consist of an intensely
heated, and either liquid or plastic thin outer shell resting upon a
cold and solid interior.

The size and position of the two recently discovered satellites of Mars,
which are believed to be not more than ten miles in diameter, the more
remote revolving around its primary very little slower than the planet
rotates, while the nearer one, which is considerably less distant from
the planet's surface than its own antipodes and revolves around it more
than three times during the Martian day, may perhaps be looked upon as
the remnants of the great meteor-swarm which completed the Martian
development, and which are perhaps themselves destined at some distant
period to fall into the planet. Should future astronomers witness the
phenomenon the effect produced upon its surface would be full of
instruction.

As the result of such an origin as that suggested, Mars would possess a
structure which, in the essential feature of heat-distribution, would be
the very opposite of that which is believed to characterise the earth,
yet it might have been produced by a very slight modification of the
same process. This peculiar heat-distribution, together with a much
smaller mass and gravitative force, would lead to a very different
development of the surface and an altogether diverse geological history
from ours, which has throughout been profoundly influenced by its heated
interior, its vast supply of water, and the continuous physical and
chemical reactions between the interior and the crust.

These reactions have, in our case, been of substantially the same
nature, and very nearly of the same degree of intensity throughout the
whole vast eons of geological time, and they have resulted in a
wonderfully complex succession of rock-formations--volcanic, plutonic,
and sedimentary--more or less intermingled throughout the whole series,
here remaining horizontal as when first deposited, there upheaved or
depressed, fractured or crushed, inclined or contorted; denuded by rain
and rivers with the assistance of heat and cold, of frost and ice, in an
unceasing series of changes, so that however varied the surface may be,
with hill and dale, plains and uplands, mountain ranges and deep
intervening valleys, these are as nothing to the div