The Breakwater in Plymouth Sound is a work of a breakwater similar nature to that of Cherbourg, but constructed on water in sounder principles, with less machinery and fewer people. Compared in extent and dimensions with that of Cherbourg, it is only in the ratio of about one to four.
There is no port and harbour on the south-west coast of England possessing so many advantages as Plymouth; none so well situated for assembling and equipping a fleet to watch the movements of the enemy in the harbour of Brest. Its dock-yard may be considered as the second in the kingdom in point of size, convenience, and effective strength; while the margin of it stretches along the magnificent harbour of Hamoaze,—a noble expanse of water, nearly land-locked, of a capacity sufficient for mooring safely a hundred sail of the line in excellent anchorage, and in water that carries its depth to the very quays of the yard. On the opposite or eastern side of the Sound, and at the distance of about three miles from Hamoaze and the dock-yard, is another sheet of water called Catwater, not quite so deep, nor so well sheltered, as Hamoaze, but, since the progress made in the breakwater, forming a safe and commodious harbour for merchant vessels of every description. These two harbours open into Plymouth Sound and Cawsand Bay, in which ships employed in the blockade of Brest, or those refitted in Hamoaze, have been accustomed to assemble and prepare for putting to sea. But the very exposed situation of Plymouth Sound, and the heavy swell that almost constantly rolled in, especially when the wind blew fresh from the south-west to the south-east, made it so inconvenient and so unsafe an anchorage for ships of the line, that, during the late war, the fleet employed in blockading Brest had been in the practice of bearing up, when driven from its station, for the more distant anchorage of Torbay, though little better with regard to security, and worse in every other respect, than Plymouth Sound. It is, for instance, a more ineligible rendezvous for the western squadron, from the chance of the fleet being caught there by an easterly wind, and unable to get out, when it is the most favourable wind for the enemy to put to sea; from the danger to which the ships are liable when so caught at an anchorage so open and exposed; and from the inconvenience, delay, and expense of obtaining the necessary supply of stores and provisions from the other ports, there being none at Torbay.—In short, this open and exposed bay bore so bad a character among naval officers, that Lord Howe used to say it would one day be the grave of the British fleet.
It is, besides, an object of the first importance to the efficiency of every naval arsenal, to have a safe and commodious roadstead in its neighbourhood, like that of Spithead to the harbour and dock-yard of Portsmouth. Here those ships which may have gone through a course of repair or refitment, or those new from the stocks, may assemble and complete their final equipment for sea; and here, also, ships returning from sea may safely lie at anchor till the wind and tide may serve them to go into harbour. But in Plymouth Sound, ships coming out of Hamoaze, or ships going into that harbour, had no such security. By the rolling sea that set in, they were exposed to the double danger of parting their cables, or striking against the hard and rocky bottom, either of which would be almost certain destruction.
It was most important, therefore, to render Plymouth Sound, if possible by any means, and almost at any expense, a safe roadstead for ships of war. To ascertain the practicability of this measure, Mr Rennie the civil engineer, and Mr Whidby the master-attendant of Woolwich dock-yard, were sent down by Lord Howick, now Earl Grey, at the suggestion, we believe, of Lord St Vincent, in the year 1806, with directions to examine and report, whether by any, and by what means, a sufficient shelter might be given to insure a safe anchorage for a fleet of ships of the line. The report was favourable; and several plans were offered for sheltering this sound, so as to render it capable of containing in safety above fifty sail of the line at their anchors. Nothing, however, was done or attempted, notwithstanding the increased and mighty preparations of the enemy, till Mr Yorke presided at the Board of Admiralty, when one of his first measures was to carry into execution this grand and important national object; the most important that perhaps was ever undertaken for the glory and the safety of the British navy. The delay that took place can only be explained by the frequent changes of the Board of Admiralty, which, we believe, have been fatal to many important measures for the benefit and advantage of this great bulwark of the nation.
Of the plans proposed for sheltering the Sound, one was to throw a pier from Staddon Point to the Panther Rock, a distance of 2650 yards; another, to construct a pier from Andurn Point to the Panther, a distance of 2900 yards; and a third, to carry a pier from the same Point to the Shovel Rock, being only 900 yards.
The objection urged against throwing out piers from either of these Points, and abutting against the shore, was principally grounded on the certain effect they would have of changing the current of the flux and reflux of the tide to the opposite side of the Sound, and of increasing its strength and velocity on that side, while it left all calm on the other; the inevitable consequence of which would be a deposition of mud or silt in the calm part or eddy, which, in process of time, would shallow the water, already not too deep, to such a degree as to unfit it for the reception of large ships of war.
Besides, of the three passages for large ships into Plymouth Sound from the sea, the two best are those on the two sides, while the worst was that in the middle. Either of the plans, therefore, which proposed piers to be thrown from the mainland, must have destroyed one of the best passages, and left the worst open, which was nearest to the anchorage behind the proposed pier. The middle passage might, in fact, be almost considered as shut up against very large ships by the St Carlos and the Shovel Rocks; whereas, if this middle passage should be shut up altogether, it would rather serve to deepen, by giving an increased velocity to the tide, which would scour out the bottom, than to shallow the two side passages.
On these considerations, Messrs Rennie and Whidby proposed that an insulated pier or breakwater should be thrown across the middle of the entrance into the Sound, having its eastern extremity about sixty fathoms to the eastward of St Carlos Rock, and its western end about 300 fathoms west of the Shovel, the whole length being about 1700 yards, or close upon a mile. They stated with confidence, that such a breakwater might, with every chance of success in its favour, be constructed; and that it would give shelter to ships in the Sound, without any danger of lessening the depth of water.
The middle part of the breakwater was proposed to be carried in a straight line for the length of 1000 yards; but they recommended that the length of 350 yards at each end should incline towards the straight part at an angle of 120°. See the figure, Plate CXXIX. These inclined ends would not only give shelter to a greater extent of the Sound, but would, in a greater degree, prevent the rushing in of the tide from agitating the water at the anchorage, than if the two extremities were left in the same straight line, and at right angles with the direction of the current into the Sound.
It was also proposed, in order to cover the Sound more effectually, that a pier should be thrown from Andurn Point towards the principal breakwater, of about 800 yards in length, with the same inclined point of 120° as the head of the breakwater. This pier, however, does not appear to have been thought necessary, and might have been in some respects injurious to the Sound. It might, however, have made Bouvisand Bay a good anchorage for frigates and smaller vessels, and given them the advantage of a fine stream of fresh water, which falls into that bay.
It was recommended, as the most practicable and best mode of constructing this great work, to heap together promiscuously large blocks of stone, which were to be sunk in the line of the intended breakwater, leaving them to find their own base, and take their own position; and it was conceived that stones of the weight of from one and a half to two tons each would be sufficiently large to keep their places, without being rolled about by the tremendous swell which, in stormy weather, is thrown into Plymouth Sound; and thus avoid the inconvenience as well as loss of time and labour which the French had experienced at Cherbourg by throwing down small rubble stones. It was thought, that, in those places where the water was five fathoms or thirty feet deep, the base of the breakwater should not be less than seventy yards broad, and the summit ten yards, at the height of ten feet above the low water of an ordinary spring-tide; in other words, that the dimensions of the breakwater in those places should be forty feet high, thirty feet across the top, and 210 feet wide at the foundation.
The surrounding shores of Plymouth Sound and Catwater were next examined, with a view to determine from what quarter materials for this great undertaking could most conveniently be obtained, as to quality, cheapness, and celerity of conveyance. On the west or Cornish side of the Sound, nothing appears but hard granite; at the head of the Sound, and in Catwater, on the Devonshire side, all is marble and limestone. In Catwater alone, it was estimated, on a rough calculation, that 20,000,000 tons might be procured in blocks fit for the work, which was about ten times the quantity that would probably be wanted. The time required for the completion of the work depended on a variety of circumstances. It is obvious that, if the two sides of the Sound had furnished proper materials for the purpose, the time would have been considerably abridged, as, in that case, when the wind was easterly vessels might deposit stones on the eastern end of the breakwater, and in westerly winds on the western extremity, and the work would thus be proceeding with an uninterrupted progress; whereas, if the stones were to be brought from one point, and that point was on the shore of Catwater, a strong southerly and south-westerly wind, those most prevalent in this country in the winter months, would generally impede and frequently render it impossible for vessels to go off with their cargoes.
Catwater, however, having many advantages, especially for the convenience of loading the vessels, and the facility of procuring blocks of any size from the quarries, was considered, on the whole, as entitled to the preference over any other place. Besides, the quarries here being in the neighbourhood of villages, lodgings and conveniences would be afforded for the workmen; and, on the whole, it was calculated that the work might be completed from hence at a cheaper rate, and perhaps in less time, than from situations much nearer to it, but much more exposed to the wind and waves.
An estimate of the expense could not be made with any degree of accuracy, as no correct section of the bottom had been taken. Supposing, however, the great breakwater to be 1700 yards in length, thirty feet in width at the top when carried ten feet above low water of spring-tides, with a slope on the southern or sea side of three feet horizontal to one foot perpendicular, and on the Sound or land side of one foot and a half horizontal to one perpendicular, it was calculated that the whole mass of stone required would be about 2,000,000 of tons. If then a hundred sail of vessels of fifty tons burden each were employed in carrying stone, and each vessel carried only 100 tons a week, the quantity deposited in one week would amount to 10,000 tons, or 500,000 tons a year, and at this rate the breakwater would be completed in four years; but making allowance for time lost in preparations, contingent delays, unfavourable weather, and deductions in the quantity of stone for the shallow parts over which the line of the breakwater was carried, the completion of the work might safely be calculated within the period of six years.
Nor would the building of the pier from Andurn Point, if so determined, increase the time of completion. If carried from the shelving rocks within the Point, leaving a passage between them, the pier would require about 360,000 tons of stone, which, by employing about thirty vessels, might be deposited in three years.
It was recommended by the gentlemen above mentioned, that the great breakwater should be begun on the Shovel and extended on both sides of it, as, by so doing, the effect produced on the Sound would be observed as the work proceeded; and that buoys should be placed along the line, so that the whole of the vessels employed might, if necessary, deposit their cargoes at the same time without interrupting each other.
The rough estimate for completing this great national work, made on the grounds above stated, was as follows:
**Estimate of the Probable Expense of a Breakwater and Pier for the Sheltering of Plymouth Sound and Bouvian Bay.**
| Item | Cost | |----------------------------------------------------------------------|--------| | 2,000,000 tons of limestone, in blocks from 1½ to 2 tons weight each, for the great breakwater, at 7s. 6d. per ton | L.750,000 | | 360,000 tons in the pier proposed to be built from Andurn Point, at 7s. | 126,000 | | Contingencies, say at 20 per cent. on the whole | 175,200 |
Total for the great breakwater: L.1,051,200
**Estimate of the Probable Expense of a Cut-Stone Pier and Two Light-houses to be built on the top of the Great Breakwater.**
| Item | Cost | |----------------------------------------------------------------------|--------| | 42,000 cubic yards of masonry, in the out and inside walls of the pier, at 27s. | L.44,700 | | 62,000 cubic yards of rubble filling between the out and inside walls, at 6s. | 18,600 | | Paving the top of the pier with large blocks of stone, 8500 square yards | 22,950 | | Two light-houses, with reflectors and argand lamps | 5,000 | | Contingencies 20 per cent | 28,650 |
Total for the pier and light-houses: L.119,900
Breakwater, L.1,051,200
Total estimate of completing the works: L.1,171,100
It was not until the opinions of the best engineers, men of science, and naval officers eminent in their profession, had been collected, compared, and seriously considered, that Mr Yorke determined to carry into execution this great undertaking. The principal objection started against it was, that it might cause the anchorage in the Sound to be destroyed in the course of time by the deposition of mud and silt along the whole eddy within it. But there does not appear to be any solid ground for this objection. The water brought by the tides from the sea is at all times perfectly clear and transparent, and that which proceeds from Hamoaze, and is supplied by the Tamar and the Tavy, is almost wholly free from any alluvial matter, these rivers holding their course through a fine granite soil. The fact is sufficiently proved by the circumstance of no deposition taking place in the recesses of Hamoaze along the dock-yard wall leading into the docks, nor in the numerous eddies that are caused by the projecting jetties and salient angles of that wall. Another objection started against the undertaking was, that by the diminish- ed quantity of water thrown by the tide into Hamoaze and Catwater, the Sound would gradually fill up, and these harbours be destroyed. But no perceptible alteration has as yet taken place in the height of the water in Hamoaze, or in the strength or set of the tides.
A rock of limestone, or rather gray marble, situated at Oreston, on the eastern shore of Catwater, consisting of a surface of twenty-five acres, was purchased from the Duke of Bedford for the sum of £10,000. Quays for shipping the stone were erected in front of it; iron railways leading from the quarries to the quays were laid down; ships were hired by contract to carry off the stone, and others built at the dock-yard. Mr Whidby was appointed to superintend the work. The quarries were opened on the 7th August 1812; the first stone was deposited on the 12th of the same month; and, on the 31st March 1813, the breakwater made its first appearance above the surface of the Sound at low water of the spring-tide. The system of quarrying the stone was conducted with admirable skill, and stones of the proper size were obtained with less waste of small rubble than might have been expected. In working these quarries an extraordinary phenomenon was discovered in the very body of the great mass of this old marble rock. At the depth of sixty-five feet from the summit of the rock, and twenty-five from the margin of the sea, a cavity, or rather a nodule of clay, was discovered, of twenty-five feet long and twelve square, or thereabouts, in the midst of which were found several bones of the rhinoceros, in a more perfect state, and containing less animal matter in them, than any fossil bones that have yet been dug out of rock or earth.
The vessels employed for carrying off the large blocks of stone were of a peculiar construction, adapted to convey with ease masses of marble weighing from three to five tons each. These great blocks of marble were placed on trucks at the quarries, and run down from thence on iron railways to the quays, against which the vessels lay with their sterns. The two stern ports were made sufficiently large to receive the trucks with the stones upon them. Each truck was passed separately through the port-hole on an inclined plane, and run to the fore-part of the vessel in the hold on an iron railway. The two sides of the hold of the vessel were calculated each to contain eight of these loaded trucks, which, at five tons on each truck, gave eighty tons of stone for one cargo. The stones thus placed on the trucks remained till the vessel arrived at the point in the line of the breakwater where they were to be deposited. By means of a crane on the deck of the vessel, the two trucks nearest to the two stern ports were then drawn up the inclined plane, and run upon a frame on movable hinges, called the typing-frame; by the falling of this frame in the manner of a trap-door the stone or stones were discharged from the trucks on the slope of the breakwater; but the typing-frame remained, by means of a catch, in the position in which it was left at the moment of discharging the stones, until the empty truck was pulled up by the crane to the after-part of the deck, from whence it was run forward to make room for the second pair of loaded trucks in the hold. The catch being now disengaged, the typing-frame returned to its former position, ready to receive the next pair of loaded trucks, and so on till the whole sixteen were discharged; and the light trucks ran upon the deck of the vessel, ready to be run out at the quay, and from thence to the quarries, to take in fresh loads of stone. In this manner a cargo of eighty tons was discharged in the space of forty or fifty minutes. The vessels were placed in the proper places for depositing the stones by means of buoys, and the exact line of the breakwater was preserved by observing lights or staves placed at a distance on the shore.
The following description, referring to Plate CXXVIII., will convey an accurate idea of these excellent vessels for the purpose for which they were constructed.
Fig. 1 shows the stern of the vessel in the act of depositing the stones. The runner R being hooked to the fore-part of the truck, raises it up, and by that means tips the stone overboard. When the stone is in the act of being drawn up out of the hold on the inclined plane B (fig. 3), the runner is hooked to the fore-part of the truck, and lashed down to the after-end over the stone, which prevents the latter from sliding off the truck in its progress up the inclined plane. The empty trucks are for the most part lodged on the fore-part of the deck, and some placed on an edge against the side of the vessel.
Fig. 2 shows the stern of the vessel when loaded, with the ports up or closed.
Fig. 3 is a longitudinal or sheer-section of the vessel when loaded, with the trucks on one side of the hold and deck, showing the number which the vessel usually stows on each side. The stones being frequently longer than the trucks, the number carried in the hold must be proportioned accordingly. In bad weather it is unsafe to send many trucks on deck; and, in general, not more than four are sent into the Sound in that way at one time; the amount of the cargoes, therefore, vary, according to circumstances, from forty to sixty-five tons; the largest stone hitherto deposited being about eight tons.
The after-part of the deck under the tiller is divided into two parts lengthways, and made to move up and down; the fore-parts are secured to a beam by hinges. This movable deck, when raised as at X, allows the stones to come out of the hold, and when down, as at Y, serves to convey the empty truck from the port to the deck, in order to make room for another stone.
D is a common windlass for heaving the trucks out of the hold up the inclined plane B.
C, the hinges of the typing-frame.
Ten vessels of this construction, for carrying large masses of stone, built in the King's Yards, and forty-three hired by contract, averaging about fifty tons each, were employed in conveying stones from the quarries. The contractors' vessels were not of the same construction as those in the immediate employ of government; they carried stones of less weight, which were hoisted out of the hold by a chain and windlass, and thrown overboard. A load of fifty tons was discharged from one of these vessels in about three hours. By all these vessels the quantity of stone deposited in 1812 was 16,045 tons; in 1813, 71,198 tons; in 1814, 239,480 tons; in 1815, 364,207 tons; and in 1816, up to 12th August, 206,033 tons, at which time the total quantity of stone sunk amounted to 896,963 tons; and at the conclusion of the year to upwards of 1,000,000 tons.
Of this quantity the proportions of the different sizes of the blocks deposited were nearly as follow:
| Size | Quantity | |---------------|----------| | Of one ton each stone, and under | 123,904 | | Of one to three tons each | 809,706 | | Of three to five tons each | 150,593 | | Of five tons and upwards | 12,760 |
The original contract price for quarrying the stone was 2s. 9d. per ton, and the original contract price for conveying it to the breakwater 2s. 10d. per ton; but the former was reduced to 2s. 5d., and the latter to 1s. 10d. per ton. The cost of each ton of stone sunk in the breakwater, including the building of quays, purchase of land, salaries, and every other expense, according to the nearest calculation that can be made, amounted to about 8s. 1½d., which, upon the whole quantity deposited, gave a total sum expended up to 12th August 1816 equal to L364,000. And as the work might be considered as more than half com- pleted, it would have been finished considerably within the original estimate; and, if parliament had thought fit to grant the money, within the time.
The greatest quantity of stone sunk in any one week was 15,379 tons; and the part of the breakwater, at the date just mentioned, above the level of low-water spring-tides, was in length 1100 yards. The length completely finished to the height of three feet above the level of the highest spring-tides, and thirty feet wide at top, was at the same time 860 feet. The large stones of the upper part of the breakwater were deposited to any nicety by means of a vessel constructed for the purpose, having the same sheer or slope at the bow with the side of the work, so that by a projecting beam or mast the largest stones could be taken out of the vessel, and placed on the opposite side, or middle, or any other part of the breakwater.
The small establishment, and the quick manner in which this great work was carried on, form a curious contrast with the multitudes employed on the breakwater of Cherbourg, the time occupied by that undertaking, and the parade and ostentation with which it was conducted.
The whole establishment for carrying on the Plymouth breakwater was as follows:
| Persons | | --- | | A superintendent, with proper officers and clerks, to keep and control the accounts | 10 | | Warrant officers and masters of the ten stone vessels in the immediate employ of the public | 21 | | Seamen and boys to navigate these vessels | 90 | | Seamen employed in the superintendents' vessels, the light vessel, boats' crews, &c. | 45 | | Masons, blacksmiths, carpenters, sail-makers, and labourers, employed at Oreston | 39 |
In the immediate pay of government | 205 | Seamen employed in the contractors' vessels | 170 | Quarrymen, labourers, &c. employed at Oreston by the contractors | 800 |
Total establishment | 675 |
The result of this great work has completely answered the expectation of its warmest advocates. The good effects of it were, indeed, very sensibly felt at the end of the second year, when about 800 yards of the central part, where the water was shallowest, were visible at low-water spring-tides. The swell was then so much broken down and destroyed at the head of the Sound, that the fishermen were no longer able as heretofore to judge of the weather outside the Sound; and ships of all sizes, and among others a French three-decker, ran in with confidence, and anchored behind the breakwater. Since that time near two hundred sail of vessels of all descriptions, driven in by tempestuous weather, have at one time found safe shelter within this insulated mole, where a fleet of twenty-five to thirty sail of the line may at all times find a secure and convenient anchorage, with the additional advantage of having a stream of excellent water from a reservoir constructed above Bouvisand Bay, capable of containing from ten to twelve thousand tons, or a quantity sufficient to water fifty sail of the line. This water is brought down in iron pipes to Staddon Point, opposite to the anchorage, where a jetty has been completed, from which the water descends through the pipes into the ships' boats. The whole expense of this most useful appendage to the breakwater is calculated at about £16,000.
During the winter of 1816-17, the gales of wind were more frequent and tremendous than had been known for many years; and, on the night of the 19th January, such a hurricane came on as had not been remembered by the oldest inhabitant. The tide rose six feet higher than the usual height of spring-tides. The Jasper sloop of war, and the Telegraph schooner, being anchored without the cover of the breakwater, were driven to the head of the Sound, and both lost; but a collier deeply laden, and under its cover, rode out the gale. No damage was sustained by any of the shipping in Catwater; but it was the general opinion, from former experience, that, if no breakwater had existed, the whole of the ships therein must have been wrecked, and the storehouses and magazines on the victualling premises, and most of the buildings on the margin of the sea, must have been entirely swept away. Till this tremendous gale the breakwater had not sustained the slightest damage from the heavy seas that, through the winter, had broken against it with unusual violence, nor a single stone having moved from the place in which it was originally deposited; but after the hurricane above-mentioned, and the high tide which accompanied it, it was found that the upper stratum of the finished part, extending about 200 yards, and thirty yards in width, had been displaced, and the whole of the huge stones, from two to five tons in weight each, had been carried over and deposited on the northern slope of the breakwater. In no other part could it be discovered that a single stone had been displaced. Since that time a considerable portion of the sea-front has been cased with masonry of immense masses of stone, but smoothly and beautifully laid; and the better to protect this, the foot of the slope is being extended seaward, in order to protect the foot of the masonry, by throwing in a great quantity of large and rubble stones, which will complete the work within the original estimate, and, it is calculated, some time in the year 1833.
The want of a harbour, or any place of safety to which Propriety ships can resort in bad weather, or in distress, between the ports of Plymouth and Portsmouth, led to the suggestion of Portland Roads being converted into a secure harbour by means of a breakwater. It was estimated that the construction of such a stone dike, extending from the north-east part of Portland Island, about two miles and a quarter in length, covering an anchorage of about four square miles, and completely sheltering the pier, harbour, and bathing place of Weymouth, would require about four millions of tons of stone, five years to complete it, and an expense of about six hundred thousand pounds Sterling. The capstone alone, which covers the Portland stone, and which, being unmarketable, is not only useless, but a great incumbrance, would be sufficient to complete this great undertaking. Such a secure anchorage in this situation, in which the largest fleets, either naval or mercantile, might ride at anchor in all winds and the most stormy weather in perfect security, is not unworthy the consideration of the public; and, perhaps, in the present increased state of our population, and the difficulty of finding employment for the labouring poor, there can be no truer policy than that of carrying on great national works of public utility, were it only for the sake of encouraging industry, instead of expending an equal, or probably a far greater sum, for the support of idleness and the encouragement of vice in those parochial buildings too frequently miscalled work-houses.