350 PHYSICAL GEOGRAPHY. 



the configuration of the coasts, and their contiguity. When the wind blows fresh, the 

 motion of the waves not being sufficiently quick, their thin and light tops are impelled 

 forward and broken, falling upon their own slopes in a torrent of white foam, particles 

 of which, in the form of spray, are carried to a vast distance by the gale. It is no un- 

 common circumstance during a violent gale, for persons far inland to be sensible of a 

 saline impregnation in the atmosphere, the spray of the waves, which have been torn by 

 the blast. In severe tempests, enormous volumes of water are accumulated in ridges, 

 which literally consist of wave on wave ; for owing to the permanence of the wind, its 

 action will raise a second upon the first, and a third upon the second, in the same manner 

 as it raised the first upon the flat surface of the water. From a number of experiments, 

 and the experience of divers, it appears that the disturbance of the sea by the action of 

 the winds, extends but a comparatively small way below the surface. The observations 

 of the Committee appointed by the British Association in 1836 show that, with a depth 

 of water equal to 12 feet, waves nine inches high and four or five feet long did not sen- 

 sibly affect the water at the bottom ; and probably at the depth of ninety feet, the sea is 

 undisturbed in the roughest weather. After the subsidence of the wind which has put 

 the surface in motion, waves continue to roll for some hours, upon the principle of the 

 pendulum swinging for some time after it has received an impulse. Hence in a com- 

 pletely calm state of the atmosphere, the ocean exhibits a great undulatory movement, 

 called the swell, which seldom entirely dies away, before the action of the disturbing cause 

 is renewed. The swell proceeds from the combined influence of winds and currents, and 

 upon the mighty oscillation being checked in its career by sand banks, or a rocky coast, a 

 roaring and violent surge is produced. Such is the surf at Madras, caused by the swell 

 of the ocean across the Bay of Bengal, a sweep of nearly five hundred miles, coming into 

 contact with the shore, where it exhibits the " wild waves' play," whose voice is heard 

 far over the level plains of the Carnatic. It frequently occurs, that while the swell is 

 advancing in one direction, the wind is blowing from an opposite quarter, or the wind 

 suddenly chops about, or the surface of the ocean receives impulses in various directions 

 from different breezes ; and in any of these cases, a series of compound waves is produced, 

 and the aspect of the deep becomes complex in the extreme. 



The Sound at Plymouth was formerly exposed to a heavy swell occasioned by the 

 south-west gales, incommoding and endangering the shipping of that great naval arsenal ; 

 but this has been remedied by the construction of the Breakwater, one of the most stu- 

 pendous undertakings ever accomplished by the genius and power of man. 



The billows sleep 

 Within the shelter of a wondrous pile 

 Of man's best workmanship that new-made isle, 

 That marble isle brought piecemeal from the shore, 

 To break the weltering waves, and check their savage roar." 



The Breakwater is a barrier or dyke, nearly a mile in length, raised above the surface of 

 the water, and stretching across the Sound so as to leave entrances at both ends. It was 

 formed by an immense quantity of large stones, quarried from some limestone hills, which 

 were shipped in vessels specially constructed for the purpose, and precipitated into the 

 sea at the spot where it was proposed to keep the waves at bay. About fifty vessels 

 were employed in this service, by which were deposited in the year 1812 about 16,000 

 tons of stone; in 1813, 71,000; in 1814, 240,000; in 1815, 264,000; in 1816, 300,000; 

 the whole quantity amounting to nearly 40,000,000 cubic feet. Baron Dupin inspected 

 this extraordinary work while in progress, and enthusiastically records the impression 

 made upon his mind by the " order, regularity, and activity which reign throughout all 

 the operations ; the embarking and disembarking of the materials ; the working and 



