A Treatise On The Principles And Practice Of Harbour Engineering

CHAPTER X. CHANNEL DEMARCATION. Value of Systematic Démarcation —Régulation and Supervision of Channel Marks—In- dependence of Authorities—Fundamental Characteristics of Signais—Beacons—Buoys —National Systems—Trinity House Régulations—Design of Buoys —-Channel Lighting ■—Luminous Buoys—Wigham Burner—Pintsch System—Lightships—Suspension of Floating Lights—Luminous Beacons and Lighthouses—Incandescent Burners—Light Concentration—Reflectors and Lenses—Catoptric, Dioptrie, and Catadioptric Systems— Range of Light—Identification of Stations—Sound Signais—Audible Buoys. Importance of Channel Demarcation.—One of the most essential features of a modern port is a clear and systematic demarcation of the channels by which it is approached from the open sea. Be the channels long or short, winding or comparatively straight, the necessity is universally and incontrovertibly evident, since, in the absence of such guidance, ships run the risk of grounding on the shoals and banks which fringe the coast-line of nearly every maritime country. Few ports are endowed by nature with an illimit- able expanse of open fairway, and, in the majority of cases, restrictions and precautions of no inconsiderable perplexity have to be observed. This is more particularly the case with those ports which lie in deep coastal and estuarine indentations, or inland upon the banks of some navigable river within the range of tidal influence. Fluctuations of depth, combined, in many instances, with the eccentricities and vagaries of currents, are a source of continuai apprehension to the mariner, who has most generally to fall back on special local assistance in order to reach his destination. Yet there are circumstances under which such assistance may not be forthcoming; and, apart from this, there is always the desirability of according harbours and ports the füllest possible measure of safe and convenient access. Too much importance, therefore, can hardly be attached to the proper and effective delimitation of navigable channels. In a maritime country one would naturally expect to find a matter of such vital interest to the community dealt with on broad and systematic lines, and the methods adopted carried to a very high state of perfection. Uniformity of practice and treatment would appear to be the most obvious of desiderata. Yet it must be confessed that, until comparatively recently, the demarcation of approacli channels was regarded, to a very great estent, as a matter of almost purely local importance, and it was largely left in the hands of 250