This invention (which we transcribe from the London Engineer) relates to a mode of simplifying the construction of foundations of piers, harbors and other submarine structures. To attain this end, a floating caisson is formed of plates of cast or wrought iron, bolted or riveted together, and this floating vessel (which is open at the upper part) is brought over the spot which is intended to receive a large block of concrete or masonry. The floating vessel being moored in the required place, concrete is discharged into it, or brick or stone-work is built up in it, as required, and by the accumulation of such building materials in the vessel the latter is sunk to a given depth in the water. The sides of the vessel are built up by adding plates of iron to the upper part of the vessel, and thus its ca- pacity and depth is increased—the upper edge of the vessel being raised considerably above the surface of the water. Fig. 1 shows a section of one of the caissons in the course of construction. A A is the outer casing, made of sheets or plates of iron, bolted together by flanges or otherwise, so as to form a vessel open at top. B is the masonry or brick-work which is being built up inside, a vacant space C being left in the middle, to give buoyancy to the vessel while its construction is proceeding. When the weight of the masonry inside has sunk the edge of the vessel to within a yard or so of the surface of the water, an additional row of iron plates are secured on its top edge, so as to increase its hight and capacity, and when this has been completed, the masonry work is proceeded with as before. The building up of the vessel in tins manner will be carried on until the bottom reaches the ground, and becomes firmly imbedded in it, when the vacant space C, will be filled in with concrete or rubble masonry. A modification of the above arrangement may be made by constructing the outer casing of sheet or plate iron, as before, but filling the interior with concrete, a vacant space being, however, left in'the center of the vessel by placing a second cylindrical or other conveniently-shaped vessel within the first, so as to render the vessel buoyant until it reaches its seat at bottom. In constructing piers, harbors, walls, or any structure projecting out from the land into the sea, it will be evident that instead of mooring the caissons or vessels while they are being constructed and filled with masonry, they may be supported by cranes, or secured to crabs iixed upon the finished part of the structure. The patentee describes in his specification several different plans for constructing the caissons or vessels inside a protecting shield, kerb, or outer vessel. Fig. 2 shows a vertical section of the simplest form of a protecting shield or casing. A A represents the inner vessel, B B the masonry or brickwork within it, and C C the vacant spaces, which are subsequently filled up with rubble, masonry, or concrete, as before explained. D D is the outer casing, constructed in the same manner as the inner one, but open at bottom, so that its lower edges may rest upon the ground and sink into it, if the ground is soft. By mooring this casing and sinking it on the desired spot, divers may be allowed to descend to the bottom and prepare the ground for the reception of the caisson or vessel which is to be constructed and sunk in it, after which the outer vessel may be raised and used for the next caisson.
This article was originally published with the title "Mode of Constructing Submarine Works" in Scientific American 13, 17, 132 (January 1858)