dy to
lose heat more rapidly in proportion as its temperature is greater.
Thus though the one-thousandth of a degree may be all the fall of
temperature that our earth now experiences in a twelvemonth, yet in
those glowing days when the surface was heated to incandescence, the
loss of heat per annum must have been immensely greater than it is
now. It therefore follows that the rate of gain of the earth's heat as
we look back must be of a different character to that of the geometric
series which I have just illustrated; for each addition to the
earth's heat, as we look back from year to year, must grow greater and
greater, and therefore there is here no shelter for a fallacy in the
argument on which the existence of high temperature of primeval times
is founded.

The reasoning that I have applied to our earth may be applied in
almost similar words to the moon. It is true that we have not any
knowledge of the internal nature of the moon at present, nor are we
able to point to any active volcanic phenomena at present in progress
there in support of the contention that the moon either has now
internal heat, or did once possess it. It is, however, impossible to
deny the evidence which the lunar craters afford as to the past
existence of volcanic activity on our satellite. Heat, therefore,
there was once in the moon; and accordingly we are enabled to conclude
that, on a retrospect through illimitable periods of time, we must
find the moon transformed from that cold and inert body she now seems
to a glowing and incandescent mass of molten material. The earth
therefore and the moon in some remote ages--not alone anterior to the
existence of life, but anterior even to the earliest periods of which
geologists have cognizance--must have been both globes of molten
materials which have consolidated into the rocks of the present epoch.

We must now revert to the tidal history of the earth-moon system. Did
we not show that there was a time when the earth and the moon--or
perhaps, I should say, the ingredients of the earth and moon--were
close together, were indeed in actual contact? We have now learned,
from a wholly different line of reasoning, that in very early ages
both bodies were highly heated. Here as elsewhere in this theory we
can make little or no attempt to give any chronology, or to harmonize
the different lines along which the course of history has run. No one
can form the slightest idea as to what the temperature of the