ilETREAT OF THE OCliAN. 



855 



or that the continents emerged, by an expansive force acting beneatli 

 them, — the effect on the water would be nearly the same. This ef- 

 fect, in scooping out valleys, has been compared to what may be ob- 

 served in miniature " by the drainage of the retiring tides on muddy 

 shores, especially in confined estuaries, where the fall is considerable 

 and rapid," the water cutting out channels for its passage, as it drains 

 off. The retiring of the ocean suddenly from the present continents, 

 would be a cause sufficient for the excavation of valleys ; but I have 

 stated, in the preceding Chapter, the reasons for believing, that con- 

 tinents emerged from the ocean, by the long continued action of an 

 upheaving or expanding force. 



The fifth theory, which ascribes the formation of valleys, and the 

 extensive denudations of the strata, to deluges that have suddenly 

 swept over different parts of the globe, has been maintained by Pro- 

 fessor Pallas and Sir James Hall. The former conjectured, that 

 the inundations that have covered parts of the Asiatic continent with 

 blocks of stone, beds of gravel, and marine remains, were occasion- 

 ed by the formation of volcanic islands in the Indian ocean. Within 

 the period of authentic history, extensive inundations have been oc- 

 casioned by volcanoes and earthquakes, which afford probability to 

 the opinion of Pallas. }n the year 1650, a new volcanic island rose 

 from the sea in the Grecian Archipelago ; and according to the ac- 

 count of Kircher, a contemporary writer, it occasioned the sea to 

 rise forty-five feet in height, at the distance of eighty miles, and de- 

 stroyed the galleys of the Grand Signior in the port of Candia. The 

 principal damage done by earthquakes to cities adjoining the sea, is 

 often effected by an enormous wave, the sea, retiring from its bed in 

 the first instance, suddenly returns with a prodigious swell, and in a 

 few moments rushes over the adjacent country. 



Sir James Hall has given greater extension and consistency to this 

 speculation. He supposes that the upheaving of a large island, like 

 Sumatra, might take place so suddenly as to drive the ocean with 

 great impetuosity over the summits of the highest mountains, and 

 strip off the glaciers, and transport them into distant countries. Ice 

 being specifically lighter than water, the glaciers would carry away 

 with them, the blocks of stone that had fallen from the impending 

 rocks, and had become encased in ice. This theory of Sir James 

 Hall's would, I conceive, offer a better explanation than any other, 

 for the occurrence of groups of fragments of particular rocks, un- 

 mixed with fragments of other rocks. Each glacier, loaded with 

 stones from the rocks above it, may be regarded as a ship freighted 

 with specimens of its native mountains, which it deposits, by thaw- 

 ing, in the place where it ultimately rests. Nor would a wave or 

 swell of the sea, that had covered the highest mountains, suddenly 

 subside ; it would sweep repeatedly over the whole surface of the 

 globe, at a lower and lower level each time; breaking down oppo- 

 sing obstacles, opening new passages for the water, and scooping out 



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