Now, what is the effect of this oscillation? Take the case to which I
have previously referred. The finer or coarser sediments that are
carried down by the current of the river, will only be carried out a
certain distance, and eventually, as we have already seen, on reaching
the stiller part of the ocean, will be deposited at the bottom.

Let C y (Fig. 4) be the sea-bottom, y D the shore, x y the sea-level,
then the coarser deposit will subside over the region B, the finer over
A, while beyond A there will be no deposit at all; and, consequently,
no record will be kept, simply because no deposit is going on. Now,
suppose that the whole land, C, D, which we have regarded as stationary,
goes down, as it does so, both A and B go further out from the shore,
which will be at yl; x1, y1, being the new sea-level. The consequence
will be that the layer of mud (A), being now, for the most part,
further than the force of the current is strong enough to convey even
the finest 'debris', will, of course, receive no more deposits, and
having attained a certain thickness will now grow no thicker.

We should be misled in taking the thickness of that layer, whenever it
may be exposed to our view, as a record of time in the manner in which
we are now regarding this subject, as it would give us only an
imperfect and partial record: it would seem to represent too short a
period of time.

Fig.4.

Suppose, on the other hand, that the land (C D) had gone on rising
slowly and gradually--say an inch or two inches in the course of a
century,--what would be the practical effect of that movement? Why,
that the sediment A and B which has been already deposited, would