Dock. An inclosed space for the reception of ships, either for their security, or for the convenience of building or giving them repairs. This word has been derived, absurdly enough, from the Greek, δοκίμιον, to receive. That we had it, along with almost the whole of our sea-terms, from the northern continental nations, is sufficiently obvious. Thus, in Flem. it is dok; Teut. dock; Swedish, docka; Suio-Goth. docka; perhaps originally from dekken, to cover, protect, secure, inclose. The dock for inclosing the prisoner in a court of justice is evidently from the same origin.
Docks for the reception of ships are of two kinds, wet and dry.
A wet dock may either have gates, to retain the water in it, so that ships shall constantly remain afloat, or be left open for the tide to flow into and ebb out of it at pleasure; either leaving it dry at low water, or with a certain depth of water remaining in it, according to its construction and situation with regard to the low water mark, and to the ebbing of the sea at spring or neap tides. A wet dock, without gates, is generally distinguished by the name of a basin, which, however, is sometimes indiscriminately applied to a wet dock, whether with or without gates.
A dry dock either becomes dry by the ebbing of the tide, when the gates are left open, or by shutting the gates at low water, and pumping out whatever water may remain in it at that time, by the power of men, horses, wind, or, which is now most commonly performed in the King's dock-yards, by the steam-engine.
A wet dock, therefore, may be defined to be "a basin of water, in which ships may be kept afloat at all times of the tide;" a dry dock a "receptacle in which every part of a ship can be examined, and its defects repaired." Ships may also be conveniently built in dry docks, and floated out by opening the gates; though, in all dock-yards, there are places set apart for this purpose, under the name of slips. A wet dock is called by the French un basin; a dry dock, une forme; and a slip, un calle.
The digging out the earth, and building the surrounding walls of masonry, to prevent the sides falling in, the preparation of the mortar and puzzolana, in the construction of a wet dock, are attended with great labour and expence. The two wet docks or basins of Cherbourg (see BREAKWATER), which are probably the finest specimens that exist in the world, are estimated to have cost three millions Sterling. The labour of excavation may sometimes be spared, and a series of wet docks or basins conveniently made by turning the course of a tide-river through an isthmus, and placing a pair of gates at each end of the old channel. In this way were the new docks of Bristol constructed, out of the bed of the Avon.
Wet Docks. Wet docks are an improvement in navigation and
commerce of the utmost importance, but of very modern date in this country; indeed, they owe their introduction entirely to a spirit of individual enterprise in commercial speculation. Liverpool might still have remained a poor fishing village, but for its convenient docks, which not only produce to the town and corporation a large revenue, but ensure to the merchant every possible facility in refitting, loading, and discharging his ships, whatever their burden or their cargo may be, without being exposed to the risk of losing both ship and cargo in a rapid tide river; and, at all events, to an unavoidable delay, occasioned by distance, the weather, or the state of the tides.
Hull is also greatly indebted for the extension of its commerce to its docks. Its old wet dock contains an area of ten acres nearly, and has accommodated at one time 130 sail of such vessels as frequent that port.
London, though unquestionably the first city in the world for its opulence, its commerce, and public spirit, and possessing within itself the powerful internal means of supporting docks, and all other conveniences that trade and shipping may require on the most extensive plans,—London has been the last to try the experiment of docks, except in the case of two spirited individuals, Mr Perry at Blackwall, and Mr Wells at Greenland Dock, both private ship-builders. Notwithstanding the total inadequacy of legal quays, which subjected the merchants to incalculable losses and delays, and in many cases proved absolutely ruinous; notwithstanding the effect of the heavy, expensive, and fatal embarrassments experienced regularly on the arrival of the West India fleets, and the annual losses, by plunder in the river, on West India produce, which, alone, were calculated to amount to £150,000 to the proprietor, and £50,000 to the revenue, and more than the double of those sums, including other branches of commerce,—it was not till the year 1799 that prejudices and private interests were so far removed, as to enable the merchants concerned in the West India trade to obtain an act of Parliament to carry into execution a plan of docks, quays, and warehouses, for the convenience of that trade, on the Isle of Dogs.
The docks of Liverpool were the first of the kind that were constructed in this kingdom, by virtue of an act of Parliament passed in 1708, and from that period the town of Liverpool has rapidly raised itself from a poor fishing village, and a port for coasting vessels, to be the second commercial town and port in the empire; and the plan of improvements now carrying into execution for the enlargement and better arrangement of the docks, will, when completed, render it, for convenience and appearance, in this respect, the very first, not London even excepted.
It appears from a statement, apparently authentic,
that, in the ten years ending with 1808, the number of ships that entered these docks was 48,497, tonnage 4,954,204; and the dock duties received L. 329,566; and that, in the following ten years, ending in 1818, the number of ships was 60,200, the tonnage 6,375,560, and the amount of duties L. 666,438. It may also be observed, that this extraordinary increase has taken place since the abolition of the slave-trade, which, it was asserted, would be the ruin of Liverpool.
The docks of Hull have also been advantageous, though in a less degree, to the wealth and prosperity of this trading town. The docks at Leith, when completed, will afford security and convenience to the increased commerce of the capital of Scotland.
The West India docks on the river Thames commenced in February 1800, and were opened in August 1802. They consist of an outward and a homeward-bound dock, and communicate by means of locks with a basin of five or six acres on the end next to Blackwall, and with another of more than two acres at the end next to Limehouse, both of which basins communicate with the Thames. The outward bound dock is about 870 yards in length by 135 in width, containing consequently an area of more than 24 acres; the homeward-bound dock is of the same length, and 166 yards in width; its area being little short of 30 acres; and the two together will contain, with ease, at least 500 vessels from 250 to 500 tons. The whole are surrounded with a high wall; and, as a security against fire, the moment that a ship enters the dock the crews are discharged, and no person whatever is allowed to remain on board, or within the premises, the gates of which are closed at a certain hour. They are surrounded by immense warehouses which are estimated to contain nearly 10,000 hogsheads of sugar, and an immense quantity of rum. The sum authorized by Parliament to be raised for completing these docks and warehouses was L. 1,200,000, and the total expence was probably not far short of one million and a half; yet on this capital, the subscribers have been receiving from a very short period after their opening 10 per cent. which, by the terms of the act, is not to be exceeded; and the term granted is limited to 21 years.
The next set of docks that were undertaken for the advantage of the trade of the capital was the London Docks. These docks are situated in Wapping, and are appropriated for the reception of all ships arriving in the port of London with wine, spirits, tobacco, and rice on board; but not exclusively, ships having on board other cargoes being admitted, on the payment of certain fees. The act of Parliament for incorporating the dock company was passed in 1800, authorizing them to raise a capital of L. 1,200,000, but such was the number of houses to be purchased (we believe not less than twelve hundred) occupying the site of the dock, that this capital, by subsequent acts, was extended to L. 2,200,000; the dividends on which are limited, as in the West India docks, to 10 per cent. The great dock is 420 yards in length, and 230 yards in width,
covering an area of 20 acres. A basin of three acres nearly connects it with the river. The warehouses are very magnificent; the tobacco warehouse is the grandest and most spacious building of its kind in the world; being capable of containing five and twenty thousand hogsheads of tobacco, and the vaults underneath as many pipes of wine. This single building, under one roof, is said to occupy upwards of four acres of ground. These docks were opened in February 1805.
The East India Docks, for the exclusive reception and accommodation of the East India ships, were the last in succession. The act for the incorporation of the Company was passed in July 1803, authorizing them to raise a capital of L. 200,000, which was afterwards increased to L. 600,000, the dividend, as in the case of the two others, to be limited to 10 per cent. These docks are situated at Blackwall. That for the reception of homeward bound ships is 470 yards in length, by 187 in width, containing a surface of rather more than 18 acres; the outward bound dock is 260 by 173 yards, and is consequently something more than 9 acres. An entrance basin of three acres nearly, and a spacious lock, connect them with the Thames.
A dry dock, requiring to be perfectly water-tight, demands the greatest care in its construction: it is sometimes lined all round with wood, but more generally with masonry, mostly of hewn granite. The expence is very considerable, as the foundation, by means of piles or otherwise, must be well secured, all leakage prevented, and the culvers or drains properly constructed, to let in and carry off the water without its undermining the quays or piers. The cost of a complete dry dock will vary probably from L. 20,000 to L. 100,000, according to the size of the ships it is intended to admit, and the nature of the ground on which it is to be constructed. A dry dock may be single, or made to contain only one ship; or double, to contain two ships; but the former is the most common, because most convenient.
As it is of the utmost importance to preserve the water in a wet dock, and to keep it out of a dry dock, it may be proper to describe the different kinds of gates that are in use for this purpose.
The most common, and, on the whole, perhaps, the best and most convenient, are swinging gates, which open in the middle, and lie flat, one part against each wharf or side-wall of the passage, leading into the dock or basin. The elevation of this kind of gate is represented in Plate LXXI. fig. 3. This kind of dock gate requires to be made of great strength, with sound timber and good iron, and the gudgeons on which the hinges turn, to be well secured into the stone abutments. Care also must be taken, to make the bottom of the passage and the bottom of the gates perfectly plane and parallel, to prevent leakage, and give facility to their opening and shutting, which is usually assisted by rollers fixed in a groove, and performed by means of a small capstern on each pier. Attached to the top of the gates is usually a foot bridge with railing, which, separating in the middle, opens and shuts with the gates.
Dock. The most simple, but by no means the most effective, contrivance for keeping out the water, is the wicket-gate, of which the plan and elevation are represented in Plate LXXI. fig. 5 and 6. It consists of three parts, which, when opened, are removed separately. This gate is rarely made use of unless where the abutments are not sufficiently strong, or their foundation sufficiently secure, to bear the weight of a pair of swinging gates.
A third kind of gate consists of a floating dam or caisson, first introduced into this country by General Bentham, and first applied to the great new basin in Portsmouth dock-yard. They are built somewhat in the shape of a Greenland fishing-boat, sharp at the two ends, narrow, and deep in proportion to the depth of water at the entrance of the dock. The keel fits into a groove at the bottom of the passage, and the two slanting ends rise and fall in corresponding grooves cut into the two abutments. Of this kind of gate, fig. 1 and 2 Plate LXXI. represent the plan and elevation. By letting in the water the caisson sinks in the grooves, and acts as a closed gate; and by pumping out the water, or letting it out to a certain depth, the dam floats, as the tide rises, and the narrow part, rising to the top, is readily disengaged from the grooves, and easily floated away as a boat. The advantages of these floating dams, as stated by General Bentham, are, that they are cheaper of construction than the gates heretofore in use for closing docks or basins; that they occupy less space, are more easily repaired, and one and the same dam is capable of being used, as need may require, in different places at different times. These caissons have also the advantage of serving as bridges of communication for loaded carriages, across the entrances they close, and require much less labour than gates, in opening or shutting up passages into docks or basins; since their occasional buoyancy may be obtained without pumping water, or unloading ballast.
Fig. 7. represents a plan, and fig. 4. a sectional elevation of a DRY or GRAVING DOCK, into which ships are taken to have their defects examined and repaired, coppered, &c. and in which, if necessary, as already observed, ships may be built.
When a ship is brought into a dry or graving dock, she gradually subsides as the water flows out, till her keel rests upon the line of square blocks, which are placed to receive it along the middle for the whole length, and on these blocks she is kept steady and upright by a number of shores and poles on each side, one of their ends being placed on the altars, or steps of the dock, the other under the ship's bends and bottom. As a ship under repair generally requires something to be done to the main or false keel, or at any rate these parts require to be inspected; sometimes to shift the main keel or to add to the whole length of the false keel, it was always found necessary, in such cases, to remove the blocks in order to get at the bottom of the ship; but this operation could not be performed without the more serious one of first lifting bodily the ship clear of all the blocks, and suspending her, as it were, in the air.
Dock. This process was performed by driving wedges simultaneously under the ends of all the shores that supported the ship; an operation that required from four to five hundred men to enable them to suspend a ship of the first rate. When the San Josef, a large three-decker, required her bottom to be examined, in 1800, the assistance of almost every artificer in the dock-yard was found necessary to perform this process of lifting her; nor was this the only inconvenience, the ship, thus suspended, suffered very material injury by the pressure of her own enormous weight against the ends of the shores that supported her, such as forcing in her sides, straining the knees and all her fastenings, breaking the treenails, &c.
To remedy these glaring inconveniences and very serious injuries that ships thus placed were apt to sustain, and to effect a saving of time and expence in the operation, Mr Seppings, then Master Shipwright, and now Surveyor of the Navy, contrived, sixteen or eighteen years ago, an improvement, as ingenious as it is simple, by which twenty men will suspend the largest ship in the navy, or rather, which amounts to the same thing, will disengage any one block that may be required in the space of two or three minutes, without the necessity of suspending her at all; and, as a first rate in dock sits upon about fifty blocks, these twenty men will clear her of the whole of these blocks in about two hours; and, as the saving of a day in completing the repairs of a ship, is frequently the saving of a whole spring tide, the docking and undocking of a ship may make, and frequently has made, by this new method, the difference of a fortnight in the time of equipping her for sea.
The block of Mr Seppings, instead of being one solid piece, consists of three wedges, or, more properly speaking, of one obtuse wedge, and two inclined planes, which, when put together and placed under the ship's keel, appear as under, when viewed in the direction or line of the keel:
where G is the wedge on which the keel rests, having its obtuse angle equal to , and HH are the two inclined planes, each having an acute angle of . The wedge is of hard wood, having its two sides lined with iron; the two inclined planes are of cast-iron. When one of these blocks is to be disengaged from under a ship's bottom, nothing more is required than a few smart blows alternately on the two sides of the two inclined planes, when they fly out, and the middle part or wedge drops, and the facility of thus disengaging any of the blocks, is in proportion to the quantity of pressure upon that block. The strokes are usually given by a kind of
catapulta or battering-ram, being a thick spar or pole moving on a pair of wheels, as KK. This sim-
ple contrivance to get at any part of a ship's bottom by removing, in succession, all the blocks without the necessity of lifting the ship, which the removal of any one block required to be done by the old method, is now universally adopted in all the dock-yards; and the Lords of the Admiralty marked their sense of the great utility of the improvement, by bestowing on Mr Seppings a reward of L. 1000 for the invention.
Another very material improvement, recently introduced into his Majesty's dock-yards, is that of covering the dry docks and building slips with roofs. The rapid decay of our ships of war by that species of disease known by the name of the dry-rot, attracted very general attention; its effects were well known, but a variety of opinions were entertained as to its causes and its cure. It was quite obvious, however, that exclusion of air and moisture were the two great operating causes in giving activity to the progress of the disease (see DRY-ROT); and that a ship in dock, stripped of her planking, and open to the weather in every part, alternately exposed to frost, rain, wind, and sunshine, must at least have her timbers differently affected, some swelled and water-soaked, others shrunk with heat, and others rifted with the wind and frost; and, if closed up with planking in this state, might be expected, at no great distance of time, to exhibit symptoms of a decay. The workmen, too, in the open docks or slips, suffered from the vicissitudes of the weather no less than the ships, and their labour was frequently suspended, to the great detriment of the naval service. The measure of roofing over the docks and slips had long and repeatedly been suggested, but either from prejudice or a false economy, it was only very recently carried into practice, but is now almost universal in all the yards. These roofs are generally constructed so as to be capable of having the sides and ends occasionally closed according to the quarter from which the wind may blow; and, by this contrivance, the timber is prevented from rifting, as it is liable to do, by the action of a thorough draught of wind, and the health of the artificer is prevented from injury. The light is admitted through numerous windows placed in the roof. These roofs are, in general, supported on a row of wooden pillars, and covered with slate, some with plates of iron, and others with shingle. Plate LXXII exhibits the transverse section of a roof thrown over the head of the dock at Plymouth, in which the Foudroyant is repairing; its
span being 95 feet 4 inches, and the extreme width 125 feet 4 inches, supported, on the principle of trussing, without a single beam. Another of the same kind is building over the Prince Regent at Chatham, whose span is 100 feet, and the extreme width 150 feet. These immense roofs are constructed after a plan of Mr Seppings. The cost of one of the dimensions above mentioned is from L. 6000 to L. 7000, which, great as it may appear, will be amply repaid by the superior quality and durability of the first ship built under it; but the same roof, with little or no repair, will, in all probability, serve as a covering for eight or ten different ships in succession. General Bentham who, in his statement of "Services rendered in the Civil Department of the Navy," seems to claim to himself all the inventions and improvements that have been introduced into the dock-yards for the last twenty years, carries his invention beyond a mere covering, and proposes to house over the docks and slips so completely, as to afford "means of heating, warming, ventilating, and artificially lighting the interior at pleasure; the introduction of boilers or steam-kilns for bending the planks, within the inclosure; the introduction of machinery for assisting in various operations, particularly the more laborious ones; the providing room for carrying on all the shipwright's work within the building; besides a variety of lesser works, such as it is found very inconvenient during the building or repairing of a ship, to have executed, for example, in a smith's or carpenter's shop at a distance." Such buildings would not only be enormously expensive, but, in the present crowded state of the dock-yards, utterly impracticable. With regard to the invention of covered docks and slips, they have been used in Venice from time immemorial; and it appeared, from the evidence given by Mr Strange, the Consul at that port in the year 1792, before the Commissioners of Land Revenue, that two-and-twenty large ships had been under covered slips, some of them for sixty years nearly. At Carlsrona, also, there are several covered docks; and both Mr Nicholls and Mr Snodgrass strongly recommended the building of ships under cover nearly thirty years ago.
Among other experiments that have recently been making in the dock-yards for facilitating and ex-
pediting the repairs of ships, one may be mentioned, of which many persons are sanguine enough to think that the successful result is likely to be attended with most important benefits to the naval service. It is that of hauling up ships of war, of any dimensions, on building slips, instead of taking them into docks. It is no uncommon practice, at various ports of this kingdom, where there are neither artificial basins nor natural harbours, to haul vessels of the burden of fifty to two hundred tons, or probably larger, upon the beach by means of capstans, to give them repairs; in like manner, most of the large fishing smacks are hauled up for security in tempestuous weather; but the practicability of hauling up ships of war, especially of the larger classes, was a matter of some doubt. Several frigates had, at various times, been hauled upon slips, when the docks were all occupied, and the ease with which the ope-
of the entrance to the Dock with Swinging Gates.