360 



CHAP. XLV. 



On the Alluvial Deposits. 



THE surface of the earth is almost every where co- 

 vered by loose materials derived from the rocks of 

 which it is formed. The general actions connected 

 with some of these have been already examined; but 

 the deposits themselves require a further notice, as do 

 the circumstances under which some of them are pro- 

 duced. And if all alluvia had formerly been consi- 

 dered as deposited on the surface, the remarks on 

 Italy have shown that there are some which have 

 been elevated together with the subjacent rocks. I 

 must therefore divide them into submarine and ter- 

 restrial. The former are necessarily antient. The 

 terrestrial may be distinguished into antient and mo- 

 dern ; being the result of the unknown actions, while 

 termed, by some, diluvium : an appellation better 

 suppressed, because connected with an hypothesis al- 

 ready rejected. The modern are the result of the dis- 

 integration of rocks in situ, of the descent of the 

 summits of hills along their declivities, and of the 

 action of existing waters ; of rivers or of the sea. 



Submarine Alluvia. 



Respecting these, I can add little to what was said 

 in the sixteenth chapter, having no further facts : it 

 remains for Geologists to investigate the districts 

 where they may be expected, and thus to extend our 

 knowledge on this important subject. Yet since the 

 rocks in general were elevated from the bottom of 

 the sea, it is more than probable that many of the 

 older alluvia belong to this species. It is difficult to 

 account for the rounding of fragments by temporary 



