district having been raised whilst the low land was accumulating at the
foot of the inland cliffs. If, instead of the bay in the diagram being
suddenly converted into a valley, we suppose with much more probability it
to be upraised slowly, then the waves in the upper parts of the bay will
continue very gradually to fail to reach the cliffs, which are now in the
diagram represented as washed by the sea, and which, consequently, will be
left standing higher and higher above its level; whilst at the still
exposed mouth, it might well happen that the waves might be enabled to cut
deeper and deeper, both down and into the cliffs, as the land slowly rose.

The greater or lesser destroying power of the waves at the mouths of
successive bays, comparatively with this same power in their upper and
protected parts, will vary as the bays become changed in form and size, and
therefore at different levels, at their mouths and heads, more or less of
the surfaces between the escarpments (that is, the accumulated beach-lines
or terraces) will be left undestroyed: from what has gone before we can see
that, according as the elevatory movements after each cessation recommence
more or less slowly, according to the amount of detritus delivered by the
river at the heads of the successive bays, and according to the degree of
protection afforded by their altered forms, so will a greater or less
extent of terrace be accumulated in the upper part, to which there will be
no surface at a corresponding level at the mouth: hence we can perceive why
no one terrace, taken in its whole breadth and followed up the valley, is
horizontal, though each separate beach-line must have been so; and why the
inclination of the several terraces, both transversely, and longitudinally
up the valley, is not alike.

I have entered into this case in some detail, for I was long perplexed (and
others have felt the same difficulty) in understanding how, on the idea of
an equable elevation with the sea at intervals eating into the land, it