Engineering Wonders of the World
Volume I

294 ENGINEERING WONDERS OF THE WORLD. Fig. 10.—MARSEILLES TRANSPORTER BRIDGE, PARTLY BUILT. 545 FEET SPAN ; HEIGHT ABOVE WATER, 165 FEET. bridges. The cost of the structure is about £22,000. The largest transporter bridge ever erected, and the first of its kind in Great Britain, is the one crossing the river Mersey and the Manchester Ship Canal between Runcorn Widnes and Runcorn, designed Transporter by Mr. John J. Webster, Bridge. M.Inst.C.E., of Westminster. (See Fig. 11.) This bridge has a span of 1,000 feet between the centres of the towers. The clear height (82 feet) from high-water level to the under side of the girders is governed by the L. and N.-W. Railway Bridge, crossing the river about 150 yards below, the girders of which have only 75 feet clearance. The principle of the bridge is the same as that of the other transporters, but the details of construction are entirely different. Two towers, built up of steel angle bars and plates, rise on each side of the river. They are square in plan, with braced legs at each corner, the width at the base being 35 feet and at the top 9 feet. The outside profile is slightly curved. The two towers are braced together horizontally and diagonally, and bolted to the top of cast-iron cylinders 9 feet in diameter, placed 30 feet apart, centre to centre. (Fig. 12.) On the Widnes side of the river the cylinders were attached to the rock, which is exposed at low water ; on the Runcorn side, eight cylinders had to be sunk through the bed of the Ship Canal to a depth of about 35 feet under com- pressed air before the solid rock was reached. (Fig. 13.) When the foundation cylinders had been fixed in position, and braced together in clusters of four with strong steel horizontal and diagonal ties, they were filled with Port- land cement concrete. The cylinders are protected by greenheart fenders, both in the river and in the Ship Canal.