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 Piraeus and of .Rhodes ; the moles of Naples, Genoa, and Castel's _mare ; the piers of Ramsgate, Margate, Folkston, .Howth, and the wooden-dike de Richlieu, thrown Across the port of Rochelle, may all be denominated Breakwaters. In French it sometimes called ,Battre d'Eau • a name which appears to have been applied to the mole at Tangier, a work com menced 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. 41(1. The term Breakwater, however, has, of •late years, been considered- as more peculiarly ap propriate to large insulated dikes of stone, whether ,of regular masonry•or sunk promiscuously in rough passes, 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 artifi harbour on a grand scale, fit for the reception of ships of war of the largest class, there are two re markable 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 neces sary, capable of being completed in the course of two years.