The genesis of the beaches is still a matter for speculation, but it may be safely affirmed that they originated as sand-bars, formed under water by wave and current action. How these bars were brought above water, so that the wind could exert its constructive power, is uncertain. A plausible hypothesis is, that while the ocean was breaking on the mainland shore and forming the Quaternary terraces, which may be seen there, sand-bars were made under water, and that the continental elevation which raised these terraces to their present position from twenty-five to eighty feet above tide, brought these sand-bars above water into a horizon of Æolian action. Once above the sea, the beaches would maintain their existence. A continued elevation of the coast would add to their seaward extent and a depression would cause a westward recession until they were brought to rest by contact with the mainland shore. In New Jersey the latter condition may be observed between Long Branch and Point Pleasant and also at Cape May. So far as it is known to the writer, the only way in which a beach can be entirely destroyed is by an inlet shifting its position. In this case the beach obliterated is replaced by the extension of an adjacent beach. Of the beaches south of New Jersey not enough is known to the writer to permit of a detailed biographical sketch. Their form and structure show that they have been subject to the same formative agencies and vicissitudes as those already described. In addition to the Georgia sea-islands of _ante-bellum_ fame, may be mentioned as familiar examples the barriers which in Virginia and North Carolina separate Albemarle and Pamlico Sounds from the ocean; in Florida, Amelia Island on which is built the city of Fernandina; Anastasia Island, in front of St. Augustine; and the beaches which separate Halifax and Indian Rivers from the Atlantic. The last named rivers are the lagoons which separate the barriers from the mainland shore. Lake Worth is one of these lagoons, of which the inlet has been closed. To what extent the Florida Keys may be included in the category of barrier beaches must be decided by future investigation. Key West is evidently a wave-built sand-bar composed of fragments of coral, molluscan shells, and foraminifera, and it seems likely that Cayo Largo and others of that type may be of similar origin. The coquina deposits of the vicinity of St. Augustine are also wave-formed. The hypothesis of Prof. Louis Agassiz, that the Florida Keys are all of organic origin--i. e., that they were formed by the growth of coral reefs--may be true so far as the determination of their location and direction. A submerged reef of coral may have formed a nucleus on which the waves and currents deposited a load of calcareous sand, but the superficial portion is evidently similar in origin to that of the beaches farther north.