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THE WORLl>. 



porary currents, produced by winds, the discharge of rivers, the 

 melting of ice, &c. 



The great oceanic currents however depend upon no tempor- 

 ary or accidental circumstances, but like the tides, on the laws 

 which regulate the motions of the heavenly bodies. The lines 

 of coast which are subjected to their continual action, are under- 

 going perpetual change, the amount of this change being depen- 

 dant upon the exposure, and the actual constitution of the coast. 

 We find everywhere, the most lofty cliffs, promontories, and pre- 

 cipices, whatever be their composition, whether like the primary 

 deposits of the Shetland isles, or like the chalk cliffs of Dover, or 

 the diluvium of Boston Harbor, all in a state of rapid and fear- 

 ful destruction, crumbling away more or less quickly according to 

 the hardness and crystalline character of the materials which 

 compose them. The whole of Boston Harbor, which is now dot- 

 ted with small islands, was once one piece of solid land. The 

 diluvium which formerly covered the rocks, has been gradually 

 worn away by the ocean, the outermost islands present nothing 

 but the bare rock, and the inner ones are now being denuded. 

 Indeed, as Prof. Hitchcock observes, when writing of the effect 

 of the ocean upon coasts- exposed to its fury, " It is difficult to 

 examine the "coast of Nova Scotia and New England, to witness 

 the great amount of naked battered rocks, and to see harbors and 

 indentations, chiefly where the rocks are rather soft, while the 

 capes and islands are chiefly of the hardest varieties, without 

 being convinced that most of the harbors and bays, have been 

 produced by this agency." To witness in perfection the immense 

 power of the waves, urged by the tempests and currents upon 

 the coasts exposed to their irresistable force, we must visit the 

 northern isles of Scotland, and behold steep cliffs hollowed out 

 into deep caves and lofty arches; and immense blocks of stone 

 overturned and carried incredible distances. In the winter of 

 1802, in the isle of Stenness, says Dr. Hibbert, a tabular shaped 

 mass of rock, eight feet two inches, by seven feet, and five feet 

 one inch thick, was dislodged from its bed and removed to a dis- 

 tance of from eighty to ninety feet ; and on Meikle Roe, one of 

 the Shetland isles,- a- mass of rock twelve feet square, and five 



