A Treatise On The Principles And Practice Of Dock Engineering

POSITION. 19 and very often the new boundaries are so irregulär as to need the exercise of inuch thought and skill in order to utilise the enclosed space to its füllest extent. Many docks owe the complexity and apparent eccentricities of their outlines to such conditions of evolution. As, however, in a treatise of this kind we must have some basis upon which to found our observations, which are to be as complété and comprehensive as possible, there is no alternative but to assume a freedom of choice and design which will rarely, if ever, be realisable in practice. Upon such an assumption the following points claim foremost attention :_________ The most convenient position, and The most suitable sliape for a dock ; The best ratio between quay space and water area; and fhat between periphery and surfac e. Position. In regard to this point certain obvious requirements im- mediately present themselves — accessibility, shelter, accommodation. Accessibihty will depend, in the first place, upon the depth of water in the approach channel. This, of course, is susceptible of improvement by artificial means, but a naturally deep fairway is a great saving in cost, both of construction and of maintenance. In the second place, accessibility will depend upon the absence of dangerous shore eddies and currents ; in the third place, upon proximity to the open sea, and, lastly, upon the range and duration of the tide. The amount of shelter will be governed by the configuration of the coast line, by the vicinity or otherwise of promontories and headlands, and by local experience in the matter of storms and cyclones. The accommodation will depend upon the area available and its disposition. Apart from considérations of exposure, a position upon the seaboard 18 preferable to one some distance up a river, for large ocean-going steamers. The navigation of a river, often tortuous in course and crowded with craft of various sizes, is a slow and, in fogs and darkness, a bazardons proceeding, rarely attended by any compensating advantages. Such ports as Antwerp and Bremen are undoubtedly handicapped by their inland situations. The disadvantage has perhaps not been fully apparent bhe Past> but it is bound to make its influence felt in the future. • oined to the difliculty of manæuvring mammoth vessels will be the attendant loss of time, which busy mercantile communities can i1l afford to endure. No doubt engineering operations are quite capable of maintaining ^.i lmProvinS tbe accessibility of these ports, but only at considérable outlay in initial and current expenditure. Ports like Marseiiles and avre, on the other hand, will always naturally enjoy the privilege of iiiect and unimpeded communication with the ocean. But it must not be wer ooked that such ports are subject to the whole violence of the open In ^me o^ storm, and that the provision of shelter from sucli destructive Renaes will often necessitate very expensive protective works. aking all things into considération, an estuarine situation is perhaps