speak more accurately, the beds which were then
accumulated will have been destroyed by being upraised and brought within
the limits of the coast-action.

Thus the geological record will almost necessarily be rendered
intermittent. I feel much confidence in the truth of these views, for they
are in strict accordance with the general principles inculcated by Sir C.
Lyell; and E. Forbes subsequently but independently arrived at a similar
conclusion.

One remark is here worth a passing notice. During periods of elevation the
area of the land and of the {293} adjoining shoal parts of the sea will be
increased, and new stations will often be formed;--all circumstances most
favourable, as previously explained, for the formation of new varieties and
species; but during such periods there will generally be a blank in the
geological record. On the other hand, during subsidence, the inhabited area
and number of inhabitants will decrease (excepting the productions on the
shores of a continent when first broken up into an archipelago), and
consequently during subsidence, though there will be much extinction, fewer
new varieties or species will be formed; and it is during these very
periods of subsidence, that our great deposits rich in fossils have been
accumulated. Nature may almost be said to have guarded against the frequent
discovery of her transitional or linking forms.

From the foregoing considerations it cannot be doubted that the geological
record, viewed as a whole, is extremely imperfect; but if we confine our
attention to any one formation, it becomes more difficult to understand,
why we do not therein find closely graduated varieties between the allied
species which lived at its commencement and at its close. Some cases are on
record of the same species presenting distinct varieties in the upper and
lower parts of the same formation, but, as they are rare, they may be here
passed over. Although each formation has indisputably required a vast
number of years for its deposition, I can see several reasons why each
should not include a graduated series of links between the species which
then lived; but I can by no means pretend to assign due proportional weight
to the following considerations.

Although each formation may mark a very long lapse of years, each perhaps
is short compared with the period requisite to change one species into
another. I am {294} aware that two palaeontologists, whose opinions are
worthy of m