The cave, the “spouting horn,” the “bridge,” the “pulpit-rock,” and other isolated islets, are all closely associated with the sea-cliff in origin. =The wave-cut terrace.=—The bottom of the sea-cliff is bordered by a submerged platform over which the water is shallow. This platform, or at any rate its landward portion, represents the area over which the water has advanced as the result of wave-cutting, and is, therefore, known as the _wave-cut terrace_. From the method of cliff development it will be seen that the wave-cut terrace is its necessary accompaniment. Such a terrace has a gentle slope to seaward, for its outer and older edge has been degraded longer and more. Its slope is influenced by the strength of the waves, being greater where they are stronger. The outer edge of the wave-cut terrace is often marked by an abrupt descent. Fig. 303 represents the wave-cut terrace in its relation to the sea-cliff above. [Illustration: +Fig.+ 311.—An elevated cliff above Great Salt Lake. In this case the water-level has been lowered. (Gilbert, U. S. Geol. Surv.)] So long as wave-cut terraces are submerged, they do not appear on topographic maps of the land, though they appear on the charts of the coasts; but if a coastal tract with wave-cut terraces be elevated, or if the sea-level be drawn down, the terraces become land. Elevated sea-cliffs and wave-cut terraces are among the best evidences of change of relative level between water and land (Fig. 311). =Wave-erosion and horizontal configuration.=—The structure of the rock along shore has as much to do with the horizontal configuration of the wave-shaped coast, as with its relief. In general, waves develop reëntrants in the less resistant portions of the shore, leaving the more resistant parts as headlands (San Pedro Point and Devil’s Slide, Pl. XX, Coast of California). It is to be noted that the resistance of rock to wave-erosion is not determined by its hardness alone. Every division plane, whether due to bedding, to jointing, or to irregular fracture, is a source of weakness to the rock, and rock of great hardness may be so broken as to offer relatively little resistance. Inequalities of resistance, whatever their cause, give origin to inequalities of coastal configuration where wave-erosion is in progress. Given a coast of marked regularity and equal exposure, but composed of unequally resistant material, the waves will make it irregular by cutting most where the material is least resistant. A regular coast of uniform material, but unequal exposure, will be made irregular by the greater cutting at the points of greater exposure. A coast of marked irregularity and homogeneous material will be made more regular by the cutting off of the projecting points, because they are most exposed. With a given set of conditions, waves tend to develop a certain sort of shore-line which, so far as its horizontal form is concerned, is relatively stable. Such a shore-line may be said to be