DISTRIBUTION OF BOULDER STONES. 353 



The loose blocks, in the different river-districts, being 

 in general separated from each other, or if any intermix- 

 ture takes place of the rolled masses of one valley with 

 that of another, it being only on their edges, it is highly 

 probable that the floods which burst from these valleys, 

 and carried along with them the masses of rocks, may 

 have been simultaneous, by which the flow of the one ba- 

 sin would bound and limit that of the other, and thus 

 prevent the water-flood of one basin flowing into the 

 neighbouring ones. 



The contemporaneous occurrence of these different 

 floods from the Alpine valleys, can alone, on this hypo- 

 thesis, explain why this aqueous flood was so generally 

 and so highly accumulated in the great valleys between 

 the Alps and the Jura, as to reach the height of most of 

 the sandstone mountains, and to a great elevation in the 

 Jura, where many blocks are found deposited. But if 

 the contemporaneous occurrence of these floods is proved 

 by the facts already enumerated, to what cause are we 

 to .refer this simultaneous bursting of floods of water 

 from so many Alpine valleys ? 



We observe, on the north-western side of the chain of 

 the Alps, numerous openings, which, by their structure, 

 seem to point out the action of violent floods. Let us 

 suppose the numerous valleys, in the districts already 

 described, closed at their present entrances, or openings, 

 as would seem from their structure to have been for- 

 merly the case; the consequence of this arrangement 

 would be the filling of the Alpine valleys with water, to 

 the height of the lowest passes among the mountains, 

 and thus an enormous accumulation of water would take 

 place. This great body of water, if let loose at once, 

 by the bursting of the lower extremities of the valleys, 



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