ENGINEERING WORKS, ETC.

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3 inches by 3 inches by inch, spaced about 2 feet 6 inches apart, whoseends are carried down, and are rivetted to the vertical and end plates ofgirders, as likewise to the outside plating; they were considered necessaryin order to withstand the great head of water the basement plating is sub-jected to; the frames were likewise braced diagonally in the direction of thelength of the dock.

Middle and floating chambers. —The System of diagonal trussing wasadopted for the middle and top chambers immediately over the latticegirders, consisting of T iron 4 inches by 3 inches by inch for the middlechamber, and 3^ inches by 3 inches by 3 /g, inch for the top chamber,having vertical plates at the top, bottom, and sides, 9 inches by J4 inch and6 inches by inch, securely rivetted to the outside plating, with angle iron2^/2 inches by 2^/2 inches by inch, and these trussing frames were tiedtogether with angle iron 2^/2 inches by 2^/2 inches by inch, thus stiffen-ing the plating. At the corners there were suitable gusset plates, andbetween each bulkhead for the middle chamber lattice work was introducedrunning longitudinally, thus binding the inside plating at the top with thebasement.

Bulkheads, &=c. —The transverse bulkheads are plated with ^ 4 -inch plateshaving angle iron 3 inches by 3 inches by inch on each side all roundthe various compartments, and are stiffened with vertical angle iron. Thecentre division plate is $/% inch thick, with angle iron on each side, top, andbottom, 4 inches by 4 inches by inch. The cellular plates at top of dockare 3 /% inch thick, with angle iron on the top and bottom, 2^/2 inches byinches by inch on each side of the plates. Manholes and doors arefitted to each bulkhead for the convenience of getting from one compart-ment to the other for inspection and painting, &c.

Plating. —The top, bottom, sides, and ends of the basement have platesyk inch thick, and double plated immediately over the lattice girders form-ing the top and bottom webs, making the sill of the dock from end to endquite flat and even; the corner angle iron for the basement being 4 inchesby 4 inches by % inch. Half way up the outside walls the plating wasxV inch, as likewise the ends and inside of the dock; all the other plateswere inch in thickness; and the angle iron for the middle chambers was3 inches by 3 inches by inch, and inch in thickness for the topchambers, placed on each side of the plates at corners.

Slope at inside. —On the sloping sides of the dock proper Steps wereformed of angle iron 2 inches by 2 inches by inch, plated over with3^-inch plates, on which were placed vertical and horizontal beams fortaking the thrust of the shoring poles.

Foot gallery. —Immediately over the sloping sides a gallery is formed ofangle-iron brackets 2^/2 inches by 2*4 inches by 3 /& inch, covered with