THEOUY OF THE EARTH. 457 



partial elevations. But I cannot allow that any such 

 temporary current, however energetic, could demolish 

 solid mountains. Thus does a full theory of denuda- 

 tion remain among the obscurities rather than the 

 hlanks of a perfect Theory of the Earth. 



The action of rivers has, from the commencement, 

 transported from the higher lands, the materials and 

 fragments of rocks, produced partly in the manner just 

 stated, and partly by their own force : thus generating 

 another class of alluvia. And these fill the cavities of 

 lakes and vallies, extend the maritime plains, excluding 

 the sea, and are, further, deposited beneath the ocean, 

 to be the germs of future solid strata. 



The sea, receiving these, receives also the fragments 

 which the action of the elements, aided by its own, 

 takes from its boundaries : thus uniting with the ope- 

 rations of rivers to enlarge alluvial shores, in return for 

 the solid ones which are demolished. And such alluvia, 

 being originally maritime, may, and do, contain marine 

 remains. But as the sea line retires, they necessarily 

 come to be found inland, and, sometimes, far removed 

 from the present ocean. Being inferior, of course, to 

 the subsequent fluviatile ones, they often also retain 

 their original levels ; yet are occasionally elevated to 

 considerable distances above that of the present ocean. 

 In both cases, they have, negligently, been ranked with 

 tertiary strata. In the latter, they are, strictly speaking, 

 elevated marine alluvia : but while they ought to be 

 distinguished from those, under this name, first enu- 

 merated, since they are not the consequence of great, 

 if partial revolutions, so is it proved that the relative 

 level of the sea and land vacillate, and that such eleva- 

 tions have been the result of this tedious and almost 

 imperceptible action. And there is no evidence of any 

 other cause of the apparent diminution, or increase, if 



