THE OCEAN. 663 



2. Effects of Oceanic Forces. 



The effects of oceanic forces are here treated under the heads of — 

 (1) Erosion ; (2) Transportation ; (3) Distribution of Material, or 

 Marine and Fluvio-marhie formations. 



1. Erosion. 



Erosion by Currents. — But little erosion can be produced by the 

 great oceanic currents, on account of their slow rate of motion, and 

 their distance from the land. Still, the Labrador current, with its 

 westward tendency (p. 40), acting against the submerged border of 

 the continent, may have produced some results of this kind in past 

 time, if not doing so now. It has been supposed that the course of 

 the steep outer slope of this submerged border (p. 11) has been deter- 

 mined by the oceanic currents ; but it is more probable that the posi- 

 tion of the slope has directed the courses of the currents. 



The tidal flow and upper wind-currents may produce results similar 

 to those of fresh-water streams of equal velocity. 



The ebbing tide and the wider-currents act on the bottoms of inlets 

 and harbors, and especially their channels, and are an important 

 means of keeping them open to the ocean, and of modelling their 

 forms. 



2. Erosion by Waves. — The waves bring to bear the violence of a 

 cataract upon whatever is within their reach, — a cataract that girts 

 all the continents and oceanic islands. In stormy seas, they have the 

 force of a Niagara, but with far greater effects ; for Niagara falls into 

 a watery abyss, while, in the case of the waves, the rocks are made 

 bare anew for each successive plunge. It is not surprising, therefore, 

 that,in regions like Cape Horn or the coast of Scotland, where storms 

 are common and the bordering seas deep, the cliffs should undergo 

 constant degradation, and be fronted by lofty castellated and needle- 

 shaped rocks. The action of the ordinary breakers is sufficient to 

 wear away rocky shores, and reduce stones to gravel and sand, besides 

 grinding the sands cf beaches to a finer powder. 



The cliffs of Norfolk and Suffolk, England, afford an example that has been long 

 under observation, as the country is one of houses and cultivated fields. Lyell states 

 that in 1805, when an inn at Sherringham was built, it was fifty yards from the sea, 

 and it was computed that it would require seventy years for the sea to reach the 

 spot — the mean loss of land having been calculated, from former experience, to be 

 somewhat less than one yard annually. But it was not considered that the slope of 

 the ground wan from the sea. Between the years 1824 and 1829, seventeen yards were 

 swept away, bringing the waters to the foot of the garden; and in 1829 there was 

 depth enough for a frigate (twenty feet), at a spot where a cliff of fifty feet stood forty- 

 eight years before. Farther to the south, the ancient villages of Shipden, Wimpwell, 

 and Eccles have disappeared. This encroachment of the sea has been going on from 



