It was proposed, therefore, to cover the side with a coating of stone 12 feet thick, to consist of blocks of 12, 15, 20, and SO cubic feet, or from one to two tons each, which casing was . to be carried to the height of 12 feet above the high water mark of the highest spring-tides ; the size of the stones to in crease towards the summit, so as to be capable of resisting the percussion of the waves, which is there. the strongest. It was calculated that this covering of 12 feet thick on both sides would require for each toise in length 70 cubic toises of stone, and that the whole length of the dike would consequent ly require 186,500 cubic toises, which, by deducting for the vacant spaces between the stones, would be reduced to 113,750 cubic toises of stone, or about one million and a half of tons. It was irther cal culated, that the expence of quarrying, the transport to the quays, the loading, conveyance, discharging machinery, together with the commissioners, clerks, &c. would coat for each cubic toise deposited on, the dike the sum of 55 lines, which for 113,750 cubic toises, would amount to 6,256,250 lines, and, adding for, contingencies 600,000 livres, the total estimate amounted to 6,856,250 livres.
The machinery employed for thus casing the breakwater may be seen in Plate XXXVII., in which, Fig. 1. Represents a section of a lighter on whiCh it is erected.
Y, three rollers of six inches diameter.
TK, two beams or sheers, moving on trunnions in grooves at T.
S, books to hold the sheers at the proper angle of inclination.
L, the axle of the windlass or wheels B, round which the rope of the pullies passes. The wheels are 12 feet in diameter.
E, the block and its hook laying hold of an iron chain round a stone.
F, the stone hoisted to the platform AZ, (fig. 1.) when the brace is unhooked at 8 ; the hoisting con tinned until the summit K of the sheers is brought to V, when they rest against the frame which sup ports the windlass ; the stone F is then lowered upon the rollers as as M, from whence it is pushed for. ward by men to the inclined plane, off which it is rolled into the water upon the side of the dike.
It was calculated that, by employing a certain number of these machines, 34,090 toises might be deposited in one year, reckoning only six working months, or 5682 toises per month, or that 487 su perficial toises of the dike might be covered in one sea son, and the whole completed in four years. Very little progress, however, bad been made at the commence ment of the war in ;803. At that period the centre of the dike only had been brought above the high water mark, in which was placed a battery and a small garri son of soldiers, the whole of which were swept away by a heavy sea, occasioned by a tremendous gale of wind in the year 1809, when all the buildings which had been erected on this part of the breakwater, the men, women, and children which composed the gar rison, together with several workmen, were washed awayat the same time, two sloops of war in the voadstead were driven on shore, and dashed in pieces.
This disaster was such as might have been expected. The effect of sinking large stones upon the small ones, already rounded by constant attrition, could not be otherwise ; the latter acting as so many rol lers, carried out the former even beyond the extre mity of the base, to which the breakwater had natu rally been brought by the action of the sea.
Of the remainder of the dike, very few parts are visible at low water; and, at this moment, the great er part is four feet below the surface of low water ; i it is sufficiently high, however, to break the force of the waves, and to make the port of Cherbourg a safe an chorage in some winds for about 40 sail of the line.
On the renewal of the war, after the rupture of the treaty of Amiens, Bonaparte began to bestow a greater share' of attention on the navy of France ; and though, for a time, the unparalleled victory of Tra falgar checked his efforts, it did not induce him to abandon them. His plans were vast, and, at the pe riod of his fall, were in rapid progress towards their completion. He had determined on • a fleet of 200 sail of the line, and the noble port of Antwerp gave him 'every facility for ship-building. Poe the better security in filming a junction of his two great Bette of Brest and Antwerp, Cherbourg now became more valuable, as .a coavenient port of retreat in case of accident; but it had no dock-yard, nor means of giving to a ship a large refit or repair. He might have thought too, as we believe most of our naval officers do, that a fleet of ships, riding at anchor behind the breakwater, are easily attackable by fire-ships, as the same wind which carries a vessel in at ona entrance will carry her out at the other, and the course would lie directly through the. centre of the fleet at anchor. Besides, it might be possible, in certain winds, under the lee of the centre part of the breakwater, to bom bard a fleet at anchor in the roadstead within it.