A cross profile of a wave-cut seashore (Fig. 5) shows two prominent features, namely, a sea-cliff with a horizontal base, and a terrace sloping seaward from the foot of the cliff. Of these, the cliff is by far the more prominent as it stands up boldly to view, while the terrace is in large part and perhaps wholly submerged. These two leading characteristics in the topography of wave-cut shores are shown in the following diagram: [Illustration: FIG. 5.--Ideal profile of a sea-cliff and current-built terrace.] The water carried landward by each wave as it rushes up the sloping surface of a terrace again finds its way seaward, either wholly or in part, as an "undertow." Much of the rock _debris_ ground fine by the ceaseless beating of the surf is separated from the coarser material, thus leaving the latter free to be moved by succeeding waves, and is carried seaward by the bottom current or undertow. During storms especially there is usually to be seen a belt of discoloured water seaward from the white breakers which margin the land. The finer _debris_ carried away from the shore by the undertow is sooner or later deposited, and much of it is laid down on the terrace bordering the land and serves to build out its seaward margin. A normal sea-terrace is thus in part the result of the cutting away of the land, and in part of the deposition of the material removed. The sea not only cuts away the land, however, but at many localities makes important additions to it. Where the water is shallow the larger waves break at a distance perhaps of several miles from the coast-line, and build up long narrow bars, usually of sand, which form barriers, more or less parallel with the shore, and shelter it from further encroachments of the sea. Again, when the wind from the sea blows obliquely to the coast, currents are established in the water which sweep along the loose material on the beach and on the submerged portion of the terrace of which the beach is a visible part, and cause it to travel in the general direction of the prevailing on-shore winds. This action also leads to the building of bars more or less parallel with the coast and at the extremities of capes, particularly where the shore currents enter deeper water and give origin to spits of various shapes, which are frequently curved towards the land and at their extremities become hooks and loops. There are thus two important processes, one destructive and the other constructive, by which the sea is continually modifying the border of the land.