A Treatise On The Principles And Practice Of Dock Engineering

40 DOCK ENGINEERING. Glasgow Docks. The dock system at Glasgow is an exemplification, also on the tridentine principle, of the method adopted in localities where gates are not rendered necessary by any considérations. The “docks”are, in fact, strictly speaking, tidal basins. The docks are in two groups. On the right hand bank, or north side of the Clyde, the Queen’s Dock has a water area of 33| acres, with 3,334 lineal yards of quay frontage, and a depth of 20 feet at low water. The entrance is 100 feet wide, and it is spanned by a single leaf swing bridge. The dock is subdivided into an outer or canting basin, 1,000 feet long by 695 feet wide, and two inner basins, the one 1,891 feet long by 270 feet wide, and the other 1,668 feet long by 230 feet wide, separated by a pier 195 feet wide. On the south side of the Clyde the Prince’s Dock has a total water area of 35 acres, with 3,737 lineal yards of quay frontage. The canting basin is 1,150 feet long, with a width of from 505 to 676 feet and there are three branch basins, each 200 feet wide, and 1,168 feet, 1,461 feet, and 1,528 feet long respectively. The north basin has a depth of 20 feet, the centre and south basins, 25 feet, and the outer basin, 20 to 28 feet below low water. The entrance is bell-mouthed in shape, with a minimum width of 156 feet, and is not crossed by a bridge.* The Kidderpur Docks, Calcutta. The tidal and fluvial conditions prevailing in the River Hooghly are irregular and conflicting. The port of Calcutta is situated some 90 miles from the sea, but the tides, when not checked by freshets during rains, exert their influence beyond that distance. “From March to July, when strong southerly winds prevail, the current at spring tides during the early poi'tion of the floods attains a velocity of 5 to 6 miles an hour. During the rainy season, when the discharge of fresh water by the branches from the Ganges is considerable, the down-stream current during the ebb tide runs at about the same rate; and during heavy freshets in the river, the upward current at the flood tide is hardly perceptible, although the level of the water is raised for many miles above Calcutta. At neap tides there is no up-stream current at all if there are freshets; the water is headed up and the level rises, but the current is always down stream. During the rains the spring tides rise to a mean height of 20^ feet, and fall to 8| feet above (zéro) datum, while neap tides rise to 15 feet and fall to about 10 feet above datum. In the dry season, which lasts from November to June, the spring tides rise to an average height of 15 feet and fall to 2| feet; while neap tides rise on an average to 12 feet and fall to 5 feet above datum. The tidal * Alston on “The River Clyde and the Harbour of Glasgow,” International Engineering Congress, Glasgow, 1901.