A Treatise On The Principles And Practice Of Dock Engineering

I8 DOCK ENGINEERING. adoption in a locality depends upon the range of tide and the meteorological conditions. In an inland sea, such as the Mediterranean, which is practically tideless, an open basin will serve all the requirements of commerce, in so far as the provision of quayage, for the reception of cargo, is concerned. Nor is there much inducement to construct closed docks when the range of tide is moderate, say not exceeding about 10 feet, instances of which occur, amongst other places, at Glasgow, Belfast, and Hamburg ; but when the rise and fall of the water level is very great, as at Liverpool, Bristol, and elsewhere, where there is a difference in level of between 30 and 50 feet, the necessity for enclosed areas, in which the water may be impounded at a fairly constant depth, becomes evident and imperative. The advantages attaching to tidal basins, where practicable, are the speedy and unrestricted arrival and departure of vessels, and the absence of costly appliances for closing the entrances. On the other hand, the main- tenance of an unchanging and uniform water level in tidal situations, is of undoubted benefit in facilitating the loading and discharging of cargoes, in avoiding the chaflng of vessels against the quayside, and in obviating the necessity of constant attention to and alterations in the moorings. Apart from the tidal question, an enclosed and sheltered dock has the advantage of providing a quiescent area unaffected by external waves and storms. In a determination of the particular design suitable for a dock or basin, such great influence is exerted by considérations of a purely local nature, and there is so much scope for the exercise of individual judgment and opinion, that it is quite impossible to lay down any hard and fast rules to be observed universally, or even in a majority of cases. Very rarely does the Engineer find himself absolutely unfettered by restrictions arising from fixed conditions, such as those relating to site, expediency, and economy. Commerce is erratic to this extent that it does not necessarily favour ports possessing admirable natural facilities for the accommodation of shipping. A port is only one of several stages in the journey from the manufacturer to the consumer. Consequently, any par- ticular merits it may possess as a harbour, are entirely subservient to its position in regard to the great trade routes. In the maintenance of well- established lines of communication much inconvenience has been endured from natuial obstacles, and large sums have been expended upon their mitigation and removal; whereas other ports, more favourably endowed by nature, have languished in obscurity. Trade, therefore, cannot be created at will ; but much may be done to induce and foster it, just as it may be injured by indifierence and neglect. It is mainly, then, within areas already occupied and probably densely populated, that provision has to be made for the formation and extension of dock accommodation. In such cases the acquisition of adjoining property has to be kept within remunerative or, at any rate, strictly utilitarian limits,