.'372 ON THE ALLUVIAL DEPOSITS. 



the solution of which is generally easy, by attending to 

 the varying courses of the waters, and to the different 

 streams which may have acted on them. The most 

 remarkable however of these terraces, are those. found 

 in the wider vallies and plains ; the deserted banks, 

 and thus the records of the former places of the river: 

 their height marking its former elevations, and their 

 positions the lateral changes of place which it under- 

 went in sinking. To enumerate the varieties in these 

 endless appearances, and to trace minutely the mecha- 

 nical causes, easy as it may be, would lead to details 

 fit only for that work on this specific subject., which, 

 having written, I here abridge. 



' Thus also would it be tedious, and, I trust, super- 

 fluous, to note what occurs in these alluvia where they 

 meet the sea or lakes : though, in the former case, it 

 must be remembered, that being a point perpetually 

 carried forwards by their deposition, these appearances 

 are often found far inland. At the actual point of 

 deposition, the effects vary according to the forms of 

 the shore; and by attending to these and to the effects 

 of the waves, we can explain the various produce, in 

 banks, spits, and islands, the filling of bays, the con- 

 version of marine inlets into fresh water lakes, or the 

 reverse, on which I formerly said all that seemed ne- 

 cessary, In the latter, the stratification of the alluvia 

 is even more remarkable than in the other deposits of 

 rivers, as might be expected : while I need not note 

 the other obvious distinctions in these cases, since they 

 are easily conjectured from many preceding remarks : 

 though it is easy to see how any lake, forming marl 

 beds, or shales, or travertine, while deep, will accumu- 

 late only alluvia at its final term; thus explaining the 

 appearances in the antient lacustral deposits, even as 

 it regards the presence of terrestrial organic fossils. I 



