HARBOURS. A harbour is a sheltered area of water wherein vessels may take refuge and may safely lie at anchor or moored to buoys. In some cases the harbour forms an intermediate access channel or sheltered anchorage lying between the open sea and the docks or quays at which the business of a port is carried on. In many harbours enjoying sufficient protection, natural or artificial, there is no definite line of demarcation between this intermediate area and that occupied by the open basins, quays and jetties where vessels berth, some convenient and well sheltered position being selected for this purpose. In some harbours there is, however, an outer protected area providing comparatively tranquil water, even in stormy weather, from which an inner harbour may be entered. The inner harbour, protected by piers or minor breakwaters, is usually provided with tidal quays at which vessels berth, as at Holyhead, or affords access to closed docks.
Harbours are necessary to all classes of seagoing vessels. The requirements of shipping do indeed vary, within wide limits, as regards the accommodation, facilities, degree of shelter and depth of water to be provided; and, whilst one harbour may be capable of accommodating all or any classes of vessel, the circumstances of another may limit its usefulness to small craft. Many tidal harbours, owing to limitations of depth, can be entered only at or near high water. Some of minor importance are dry, or nearly dry, at low water, and vessels using them must take the ground. The present article describes some of the more important and typical examples, both natural and artificial, the principles on which artificial harbours are—or should be—planned, and the means by which natural facilities have been improved and supple mented by artificial works. The guiding principles to be followed in the making of small harbours are the same, mutatis mutandis, as those which are applicable to the great achievements of mari time engineering construction on which millions of money have been expended.
Breakwaters, which constitute the principal protection works of most artificial harbours, are described in a separate article; for the interior works and facilities of a port see Docxs ; river and estuarine harbours are also referred to in the article RIVER ENGI NEERING; and for the lighting and buoying of harbours see LIGHT HOUSES and BUOY. See DREDGES AND DREDGING and JETTY and further particulars of individual harbours under place names, e.g.,