Science, Geology and Physics 



convulsed. The world, it is presumed, furnishes no example of 1822 

 similar agitation. The river does not, however, boil, in the Wlg 

 common acceptation of that word, at all. The whole surface, 

 and probably all beneath it, is a body of foam, differing essen- 

 tially from what I have seen produced elsewhere, and much 

 more strongly indicating the immense force of the current. The 

 bubbles, of which it is universally composed, are extremely small ; 

 and appear continually ascending, and spreading on the surface, 

 in millions of irregular circular areas. These are all limited by 

 lines, formed by chains of the larger bubbles, stretching between 

 the several areas, so as to mark distinctly the extent of each. 

 The lines themselves fluctuate unceasingly ; and, while they con- 

 tinually change their form, more along the surface, also, in every 

 direction. Thus the whole river appears in one common con- 

 vulsion, as if affected with a deep, paralytic tremor, reaching from 

 shore to shore, as far down the stream, as the eye can trace it, 

 and apparently from the surface to the bottom. To give you the 

 impression, which it made on my mind, I think of no better 

 method, than to say, that it seemed as if a vast volcanic struggle 

 had commenced beneath this world of waters, whose incumbent 

 weight hitherto prevented the approaching explosion. 



The cause of this singular phenomenon may be thus under- 

 stood. Immediately below the precipice, the bed of the river 

 where it receives the falling sheet, is of immense depth. Into this 

 receptacle the mass of descending water, plunging from such a 

 height, forces its way to the bottom. Here, forming a curve, it 

 begins to ascend. The current is, however, checked in every stage 

 of its progress by the immeasurable weight of the superincumbent 

 water. The motion upward must therefore become slow, 

 divided, and irregular. In these circumstances, instead of a cur- 

 rent, there must obviously be a general agitation, an universal 

 heaving ; such, as might be expected from the throes of an earth- 

 quake. As the ascending current is thus broken, and enervated, 



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