The direction of the diagonal inclination in the different terraces being
different,--in some being directed more towards the middle of the valley,
in others more towards its mouth,--naturally follows on the view of each
terrace, being an accumulation of successive beach-lines round bays, which
must have been of different forms and sizes when the land stood at
different levels: for if we look to the actual beach of a narrow creek, its
slope is directed towards the middle; whereas, in an open bay, or slight
concavity on a coast, the slope is towards the mouth, that is, almost
directly seaward; hence as a bay alters in form and size, so will the
direction of the inclination of its successive beaches become changed.

(FIGURE 11. DIAGRAM OF A BAY IN A DISTRICT WHICH HAS BEGUN SLOWLY RISING)

If it were possible to trace any one of the many beach-lines, composing
each sloping terrace, it would of course be horizontal; but the only lines
of demarcation are the summit and basal edges of the escarpments. Now the
summit-edge of one of these escarpments marks the furthest line or point to
which the sea has cut into a mass of gravel sloping seaward; and as the sea
will generally have greater power at the mouth than at the protected head
of the bay, so will the escarpment at the mouth be cut deeper into the
land, and its summit-edge be higher; consequently it will not be
horizontal. With respect to the basal or lower edges of the escarpments,
from picturing in one's mind ancient bays ENTIRELY surrounded at successive
periods by cliff-formed shores, one's first impression is that they at
least necessarily must be horizontal, if the elevation has been horizontal.
But here is a fallacy: for after the sea has, during a cessation of the
elevation, worn cliffs all round the shores of a bay, when the movement
recommences, and especially if it recommences slowly, it might well happen
that, at the exposed mouth of the bay, the waves might continue for some