The general result of wave-erosion is the advance of the sea on the land, the rate of advance being determined chiefly by the nature of the material attacked and the strength of the waves. Numerous as examples are of the retreat of coast-lines before the advance of the sea, it is not to be understood that the advance of the sea on the land is universal or uninterrupted. Numerous instances may be cited of the encroachment of the land on the sea. At Long Branch the advance of the sea, in spite of elaborate breakwaters, has been so rapid in recent years as to menace important buildings, while a few miles to the north and south, the land is advancing in the face of the waves. The low coast of the Middle Netherlands has retreated two miles or more in historic times,[160] but the opposite tendency is shown at other points in the same region. On the coast of England the sites of villages have disappeared by the advance of the sea within historic times,[161] but the coast of the same island affords illustrations of land advance. On the south side of Nantucket island, the sea-cliff has been known to retreat before the waves as much as six feet in a single year.[162] Almost every considerable stretch of coast affords illustrations both of the advance of the sea on the land and of land on the sea; but in the long run, the former must exceed the latter, diastrophic movements aside. [Illustration: +Fig.+ 305.—Steep cliff developed by waves. Allen Point, Grand Island, Lake Champlain. (Perry.)] [Illustration: +Fig.+ 306.—Cliff in unconsolidated material (bowlder clay), with lake-beach in foreground. South Manitou Island, Lake Michigan. (Russell, U. S. Geol. Surv.)] [Illustration: +Fig.+ 307.—Steep cliff in unconsolidated material, the result of rapid cutting. Southeast extremity of Grove Point, Md.] _Topographic Features Developed by Wave-erosion._ [Illustration: +Fig.+ 308.—Standing Rock. A wave-erosion monument. West shore of Random Sound, south of Clarenville, N. F. (Walcott, U. S. Geol. Surv.)] =The sea-cliff.=—The action of the waves, cutting as they do along a definite horizontal zone, has been compared to the action of a horizontal saw. As the waves cut into the shore at and near the water-level, the material above, being unsupported, falls, leaving a steep face above the line of cutting. This steep face is known as _the sea-cliff_ (Figs. 301 to 306). The same term is sometimes applied to the cliffs of lakes. The principles involved in the development of the sea-cliff are applicable to any broad stretch of water.