A Treatise On The Principles And Practice Of Harbour Engineering

HARBOUR DESIGN 9 spirit of all scientific procedure. Our endeavour, therefore, in the following pages will be to collate such data as are definitely acceptable, to elucidate as far as possible those problems which present themselves within the range of ordinary experience, and to lay down certain rules which may serve for general guidance to those engaged in adapting some of the most variable forces in nature to the use and service of man. A clear conception of our purview is essential, so we must commence with one or two definitions. Classification. -A harbour is primarily a place of rest and refuge—a place where safety and hospitality are to be found. But round this central idea have grown several accretions of meaning, the gradations of which it is desirable to point out. Limiting our references, as is natural and proper, to the domain of navigation, we may observe that a vessel seeking shelter under stress of wind and weather may possibly obtain it as follows : — (1) Within a tract of water, not necessarily inclosed in any way, even partially, but adjacent to or not far distant from the coast-line, where there is good holding-ground for anchors and some protection from the onset of heavy seas. Such conditions constitute a Roadstead. Roadsteads may be either natural or artificial. In the case of a natural roadstead, a deep channel, with an intervening bank or shoal to seaward, possesses the necessary characteristics, as exemplified in the offing of the Port of Ostend (fig. 1). An artificial roadstead may be created on similar lines by a breakwater, either parallel to the coast, or curvilinear, such as that at Zeebrugge (fig. 2). (2) Within a definitely circumscribed area, almost completely inclosed, either naturally, as in the case of a creek or estuary, or artificially, by