Engineering Wonders of the World
Volume III

68 ENGINEERING WONDERS OF THE WORLD. the Tyne was founded on a rubble base, which, at the outward end of the pier, had its crest 27 feet below water ; the top of the mound was protected by an apron of 41-ton concrete blocks ; yet winter storms drew out blocks until it became necessary to rebuild 1,500 yards of the pier. be dealt with, of the materials and local labour available, and many other points, each of which demands careful and minute in- vestigation.” For localities where tides are small, as at Portland, Plymouth Sound, and Cape Town, the rubble mound form of breakwater is well A TITAN SETTING A 40-TON APRON BLOCK AT SOUTH SHIELDS BREAKWATER. Crane built by Messrs, Stothert and Pitt, Bath. A thorough investigation of the physical conditions of the site must precede the prepa- ration of a design for a harbour. To quote Sir William Matthews : “ This Preliminary examinafjon should have spe- Investigation. . cial reference to exposure, the set and velocities of the currents, the possibility of shoaling consequent upon the proximity of accumulations of sand or shingle, the nature and depth of the shelter required and its extent, the character of the strata to wall, formed Portland Cement. suited. On the score of rapidity of construction and minimum cost, the concrete either of mass concrete moulded in situ, or of blocks manufac- tured in special yards and carried to the spot, is now adopted widely. It is not overstating the case to say that the discovery of Portland cement has revolution- ized the art of harbour construction, by fur- nishing the engineer with a ready means of overcoming the violence of the ocean by the