Engineering Wonders of the World
Volume III

HARBOUR CONSTRUCTION. 73 LOWERING A 40-TON BLOCK, DOVER HARBOUR. ably in mass that just described. It is 7,860 feet long, and has a greatest width at bottom of 460 feet, and a maximum Holy head of about 65 feet, in- Breakwater. . ’ eluding the wall built on the rubble mound. The engineer, the late Mr. J. M. Rendel, was enabled, owing to the land connection, to use trucks running on stagings supported by piles for carrying the stone to the dumping spot. The wagons had flap bottoms, through which the stones were dropped. As soon as the waves had con- solidated the mass, and brought the slopes to the natural “ angle of repose,” the super- structure, two walls enclosing a hearting of rubble masonry, was built. The seaward face of the wall is protected at the foot by the large rubble covering th© top of the mound. The year—1847—in which the Holyhead breakwater was begun also witnessed the com- mencement of the breakwater at Alderney, which is remarkable as being formed near trouble owing to Alderney j. ,, _ _ Breakwater, oi the mound be- the terrific pounding it received the head in a depth of 133 feet below low water at ordinary spring tides. The super- structure, a wall 59 feet high, gave much settlements low and to from large stones of the mound during storms. This breakwater cost £1,217,000, or about £200 for every lineal foot. Passing now to Ireland, we should notice the breakwater on the south side of Dublin Har- bour. The foreshore (sea slope) of this was originally faced with granite blocks, the largest of which weighed 6 tons. These were gradually broken up and re- moved by the waves; so in 1862, Mr. B. B. Stoney replaced them with 50-ton concrete blocks, which sufficed until, in 1873, a storm pulled one out, moved it 30 feet, and turned it completely over. Determined to effect permanent repairs, Mr. Stoney prepared on Immense Blocks at Dublin.