66 



of elephantina have probably no more changed 

 their absolute heig ht during thousands of years, 

 than the summits of Mount Blanc and of Ca- 

 nigou. When you have closely inspected the 

 great scenes of nature in different climates, it is 

 impossible not to admit, that those deep clefts, 

 those strata raised on end, those scattered 

 blocks, those traces of a general convulsion, are 

 the results of extraordinary causes, very different 

 from those which act slowly on the surface of 

 the globe in it's present state of tranquillity and 

 repose. What the waters carry away from the 

 granite by erosion, what the humid atmosphere 

 destroys by it's contact with hard and unde- 

 com posed rocks, almost wholly escapes our 

 perception ; and I cannot believe, as some geo- 

 logists admit, that the granitic summits of the 

 Alps and the Pyrenees lower in proportion to 

 the accumulation of pebbles in the gullies at the 

 foot of the mountains. In the Nile, as well as 

 in the Oroonoko, the rapids may diminish their 

 fall, without the rocky dikes being perceptibly 

 altered. The relative height of falls may be 

 changed by the deposits of mud formed below 

 the rapids. The beds of rivers, on account of 

 the action of the currents, tend incessantly tow- 

 ard a kind of curve, upon which depends w T hat 

 is called the stability of the bed ; and this stabi- 

 lity can be affected only by the transport of 

 friable matters, which the waters carry away, 

 vol. v. F 



