Engineering Wonders of the World
Volume III

HARBOUR CONSTRUCTION. A HUGE TITAN CRANE LIFTING A 35-TON LOAD. {Photo, Messrs. Ransomes and Rapier.) Working radius, 67 feet. Weight, 320 tons. and so expend its energy in climbing. When its force is exhausted, the wave falls back on Methods of Wave- stopping. the slope and rushes down again, its momentum assisting to stem the violence of the succeeding wave. The second method is to employ a more or less vertical wall, which suddenly converts horizontal into ver- tical motion. The wave, on reaching the face, climbs up it, and then sinks, causing a sea- ward reflection of the undulating movement. The effects of a wave are comparatively slight below the trough, and . ... decrease rapidly with the depth. Hence below low-water level rubble mounds can be given a steep pitch, and be made of smaller stones than would be needed at and above water level. This is the general rule. But there are instances to prove that wave action extends, under certain con- ditions, to a much greater depth than was once supposed. Sir William Matthews, the celebrated harbour engineer, records that at Peterhead breakwater, during a storm in 1898, blocks weighing upwards of 41 tons were displaced at a level of nearly 37 feet below low water of spring tides, and that a section of the breakwater, weighing 3,300 tons, was slewed bodily two inches without breaking the joints. It is estimated that to effect this a pressure of two tons per square foot below as well as above normal water level must have been required. The same authority also re- lates that the north pier at the entrance to