BREAKWATER, is any obstruction of wood, stone, or other material, as a boom or raft of wood, sunken vessels, &c., placed before the entrance of a port or harbour; or, any projection from the land into the sea, as a pier, mole or jetty, so placed as to break the force of the waves, and prevent their action on ships and vessels lying at anchor within them. Thus, the piers of the ancient Piræus and of Rhodes; the moles of Naples, Genoa, and Castellamare; the piers of Ramsgate, Margate, Folkstone, Howth, and the wooden-dike de Richlieu, thrown across the port of Rochelle, may all be denominated Breakwaters. In French it is sometimes called Battre d'Eau; a name which appears to have been applied to the mole at Tangier, a work commenced in 1763, under the direction of Lord Ti-viot, Sir J. Lawson, and Sir Hugh Cholmley, and finished, or rather discontinued, in 1776, after having cost this nation the sum of L. 243,897, 5s. 4½d. The term Breakwater, however, has, of late years, been considered as more peculiarly appropriate to large insulated dikes of stone, whether of regular masonry or sunk promiscuously in rough masses, so placed, as to form an artificial island across the mouth of an open roadstead, and thereby, from obstructing and breaking the waves of the sea, to convert a dangerous anchorage into a safe and commodious harbour for the reception of ships of war or merchantmen.
Of this description of dike, for creating an artificial harbour on a grand scale, fit for the reception of ships of war of the largest class, there are two remarkable examples in the Breakwater of Cherbourg and that of Plymouth,—the one after thirty years of almost uninterrupted labour still very far from being completed; the other, in the course of about four years, in a much more forward state, and if necessary, capable of being completed in the course of two years.