[Footnote: It is thought probable that this process is complete,
or nearly so, in the moon. If this be the case, it is in all
probability in progress in the case of the earth, though, owing to
the much greater bulk of the latter, it occupies a longer period.
--Lockyer, Lessons in Astronomy, p. 93.] be declining in intensity;
but the rate of that decrease is unknown; it may be in
arithmetical, or it may be in geometrical progression. It is,
then, by no means impossible that changes, which now only become
discernible with the lapse of centuries, might, at some past
period of our globe's history, have been the work of years only.
Nor is it at all probable that the present rate of change, which
is assumed as the basis of the calculation, is known with any
approach to accuracy. Exact observations are of very recent date;
both the inclination and the means for making them are the growth
of the last two centuries, and the changes which have to be
ascertained are of a class peculiarly liable to modification from
a variety of local and temporary causes, so that a very much
longer period must elapse before we can arrive at average values
which may be relied on as even approximately accurate.

Another circumstance, which seems to merit more attention than it
has received, is the very frequent recurrence in Greek mythology
of allusions to creatures which have been usually regarded as the
creations of a poetic fancy, but which bear a strong resemblance
to the Saurian and other monsters of the Oolite and Cretaceous
formations. Of course, it is not impossible that these things may
have been purely poetic imaginings; but, if so, it is very
remarkable that such realizations of those imaginings should be
afterwards discovered. It would seem much more probable that these
legends were exaggerated traditions of creatures which actually