INEQUALITIES OF SEDIMENTATION 343 



sand to fill a triangular area between the coast line and a breakwater running 

 out 1,200 yards from the shore. No sooner, however, were the works 

 commenced than it became obvious that the above estimate of sand travel 

 was completely unreHable. The wave-borne sand travelling up from the south 

 was about sixty times greater in volume than the corresponding amount brought 

 down by the northeast monsoons. The original estimate of sand in motion was 

 243,000 tons per annum; a second estimate in 1904 was 550,000 tons per 

 annum. The accumulation at the present time shows that about 1,000,000 

 tons per annum travel along the coast line. Low-water line between 1876 

 and 191 2 has crept seawards for a distance of 2,500 feet. In 1881 a terrific 

 cyclone wrecked the harbour works then nearly completed but a somewhat 

 similarly outlined harbour has since been carried out on altered lines. For 

 a distance of more than 3 miles severe erosion has taken place on the north 

 side of the harbour due to the arrest of the normal volume of travelling sand, 

 and whole towns and villages have thus been swept away. This experience 

 is an extreme instance of the action which goes on in a greater or less degree* at 

 every headland, river-mouth or solid projection from a foreshore into the 

 sea.^ 



It may be noted here that the migration of clastic materials 

 in the Kttoral zone is not confined to the finer products of erosion 

 but comprises much coarse material and even heavy blocks of 

 stone. 



Rollers bring in shingle and sometimes large masses of rock from deep 

 water. It frequently happens that, after a severe gale in the channel, boulders 

 weighing several hundredweight will be found strewn along the strand. These 

 are mostly weed-covered. The growth of weed evidences the fact that the 

 action of the waves has reached sea depths normally tranquil. In exposed 

 portions of the coast fine of Scotland boulders upwards of 2 tons in weight are 

 similarly thrown up after storms and their occurrence on these spots is so much 

 a matter of course that they go by the name of "travellers. " Their buoyancy 

 being increased by the crop of seaweed they carry, they are pushed along the 

 sea bed under the impulsion of the deep-water rollers. As an instance of deep- 

 sea wave action may be cited the fact that concrete blocks at Peterhead 

 harbour weighing 47 tons were forced out of position at a depth of 40 feet 

 below low water.^ 



The English Channel is an area over much of which clastic 

 sediments pass without stopping to build up formations. The 

 detailed explorations of the bottom of the English channel made by 



'A. E. Carey, "The Sanding up of Tidal Harbours," Proc. Inst. C.E., CLVI 

 (1903-4), 1-90; A. E. Carey and F. W. Oliver, Tidal Lands. Blackie & Sons, Ltd., 

 (i9i8),pp. 144-45- 



'Op. ciL, p. 150. 



