DOCK . established on the See also:

• SEA (in O. Eng. sae, a common Teutonic word; cf. Ger. See, Dutch Zee, &c.; the ultimate source is uncertain)
• SEA, COMMAND OF THE

The two deep arms of the sea at New See also:

• YORK
• YORK (HOUSE OF)
• YORK, EDMUND OF LANGLEY, DUKE OF (1341-1402)
• YORK, EDWARD
• YORK, FREDERICK AUGUSTUS, DUKE OF (1763-1827)
• YORK, RICHARD, DUKE

See also:

• SOUTHAMPTON
• SOUTHAMPTON, EARL OF
• SOUTHAMPTON, HENRY WRIOTHESLEY, 3RD EARL OF (1J73—1624)

7). The most recently constructed Liverpool docks, also, at the northern end have been given this form ; and the older docks adjoining them to the south have been transformed by reconstruction into a similar series of branch docks opening into a dock alongside the river wall, leading to a half-tide basin or river entrances (fig. I). The Manchester and See also:

• SALFORD

In this manner, by meansof an inner pair of gates, the basin can be used as a large lock without unduly altering the water-level in the dock, and saves the delay of locking most of the vessels out and in, the lock being only used for the smaller vessels leaving See also:

• EARLY
• EARLY, JUBAL ANDERSON (1816-1894)

Where a dock is partially or wholly constructed on reclaimed land, the reclamation bank for enclosing the site and excluding the tide has to be undertaken first by tipping an See also:

• EMBANKMENT

Or the soft stratum can be enclosed with a See also:

• DOUBLE
• DOUBLE (from the Mid. Eng. duble, the form which gives the present pronunciation, through the Old Er. duble, from Lat. duplus, twice as much)

At tidal ports, however, an addition has to be made equal to the difference in height between the high-water levels of spring and neap tides; so that at ports with a large tidal range, such as the South Wales ports on the Severn estuary and Liverpool, specially high dock walls are necessary. Under normal conditions, a dock wall should Dock Wall. be given a width at a height half-way between dock-bottom and quay-level', equal to one-third of its height above dock-bottom, and a width of half this height at dock-bottom. Dock walls are constructed of masonry, See also:

• BRICKWORK

To reduce the amount of filling behind the wall,thc+ excavation at the back above dock bottom, preparatory for the trench, is given as steep a slope as practicable, supported sometimes towards the base by timbering and struts; but occasion- ally the wall is built within a timbered trench carried down to the required depth, before the excavation for the dock in front of it has been executed; as effected at Tilbury. The filling at the back is thus reduced to a minimum, and the lower portion of the excavation can Wall. ent, after the See also:

• ADMISSION

Compressed See also:

• AIR (from an Indo-European root meaning " breathe," " blow ")
• AIR, or ASBEN

Thus the walls along the Seine, and round the basins at Rouen, were built upon bearing piles carried down through the alluvial bed of the river to the chalk. The lower portion of the quay wall was constructed of concrete faced with brickwork within water-tight timber caissons, resting upon the piles at a depth of 91 ft. below low water; and upon this a rubble wall faced with bricks was erected from low water to quay-level, backed by rubble stone laid on a timber flooring sup-ported by piles, together with chalk, to form a quay right back to the top of the slope of the bank of the deepened river (fig. 17). The quay walls of the open basins bordering the t Hudson river at New w o T. `.:~',~~!y1~e~~~-~~r,-g.~a.i York have had, in cer- See also:

• TAIN

At Southampton, ferro-concrete piles were employed in constructing the deep quays; and a wharfing of timber pilework has been frequently used for river quays. Where the increase of trade is moderate and the conditions of the traffic permit, and also at coal-shipping ports, See also:

• ECONOMY

To avoid this, the water is some- times replenished from some clear inland source, an arrangement adopted at some of the South Wales ports opening into the muddy Severn estuary, and at the Alexandra dock, Hull, to exclude the silty See also:

• WATERS, TERRITORIAL

When full, this is lowered to the bottom of the hold and emptied, thereby gradually forming a See also:

• CONE (Gr. Kwvos)

; the " See also:

• CAMPANIA

Moreover, in spite of the great range of tide at the South Wales ports on the Severn estuary, the available depth at high water of neap tides of 25 ft. at the Roath lock. Cardiff, was increased in the lock of the new dock to 311 ft.; the depth at the entrance to the Barry docks, opened in 1889, was 291 ft., but at the lock opened in 1896 was made 411 ft.; whilst a depth of 34 ft. has been proposed for the new lock of the Alexandra dock extension at See also:

• NEWPORT

On the other hand, they are accessible for a more limited period at each tide than locks; and they do not allow of the exclusion of silt-bearing tidal water, and therefore necessitate a greater amount of dredging in the docks, and especially in half-tide basins, for maintenance. Entrances, however, at large ports are frequently supplemented by the addition of a lock at some convenient site, rendering the ports accessible for the smaller class of vessels for some time before and after high water, as for instance at Liverpool, Barry, Havre and St Nazaire. A. small basin with an entrance at each end—an arrangement often adopted—is in reality, for all See also:

• PRACTICAL

When the range of tide at a port is large, and the depth in the approach channel is sufficient to allow vessels to come up or go out some time before and after high water, and also where the water in the dock is kept up to a high level from an inland source to exclude very silty tidal water, it is expedient to reduce the cost of construction by limiting the depth of the excavations for the dock, and consequently also the height of the dock walls, to what is necessary to provide a sufficient depth of water below high water of the lowest neap tides, or below the water-level to which the water in the dock is always maintained, for the vessels of largest draught frequenting the port, or those which may be reasonably expected in the near future. The upper sill of the lock is then determined by the level of dock-bottom; but the lower sill is taken down approximately to the depth of the bottom of the approach channel, or to the depth to which it can be carried'by dredging, so as to enable the lock to admit or let out at any time all vessels which can navigate the approach channel. Thus, for instance, the outer and intermediate sills of the lock at the Barry docks are 9 ft. lower then the upper sill. The foundations for the sill and side walls at each end of a lock, and also for the side walls and invert commonly enclosing the lock-chamber at the sides and bottom, are generally constructed simultaneously with the dock works, under shelter of a cofferdam across the entrance channel, and in the excavations kept dry by means of pumps. The foundations under the sills and adjacent side walls are carried down to a lower level than the rest, and iff possible to a water-tight stratum, to prevent infiltration of water under them owing to the water-pressure on the upper side of the gates; or sometimes one or two rows of sheet piling have been driven across the lock under the sills to an impermeable stratum, to stop any flow. The foundations for the sills consist usually of concrete deposited in a trench extended out under the adjoining side walls. The sill, projecting generally about 2 ft. above the adjacent gate floor over which the gates turn, is built of granite; and the same material is also used for the hollow See also:

• QUOINS (an old variant spelling of " coin," from Lat. cuneus, a wedge)

Owing to the alluvial stratum at the site of the lock close to the Seine estuary, of which it doubtless at one time formed part, the foundations for the sill and side walls or heads at each end of the lock were executed by aid of compressed air. The foundations for these heads were carried down to an impermeable stratum by means of two bottomless caissons, filled eventually with concrete, 2131 ft. 362 long across the lock and 105 ft. wide in the line of the lock at the upper end,, and 206, ft. long and i i64 ft. wide at the lower end, to a depth of 18 ft. below the sill at the upper end, and 41 ft. at the lower end, owing to the See also:

• DIP (Old Eng. dyppan, connected with the common Teutonic root seen in " deep ")

See also:

• GREEN, A
• GREEN, ALEXANDER HENRY (1832—1896)
• GREEN, DUFF (1791—1875)
• GREEN, JOHN RICHARD (1837—1883)
• GREEN, MATTHEW (1696-1737)
• GREEN, THOMAS HILL (1836-1882)
• GREEN, VALENTINE (1739–1813)
• GREEN, WILLIAM HENRY (.1825–1900)

By curving the gates Dock Gate. of the chamber. - The gates closing the entrances and locks at docks are made of wood or of iron. In iron gates, the heelpost, or a vertical closing See also:

• STRIP

25). Being, however, simple in construction, taking up little space, and requiring no chamber or machinery for moving it, this form of caisson is generally used for closing the entrance to a graving dock, where it remains for several days in place during the. See also:

• EXECUTION (from Lat. ex-sequor, exsecutus, follow or carry out)

Gates in wide entrances or locks are generally sup-ported towards their outer end by a See also:

• ROLLER

The caisson itself also serves as a very strong movable bridge, and therefore is often preferred at See also:

• DOCKYARDS

Water is admitted into the See also:

• PONTOON (Fr. ponton, from Lat. pons, a bridge)