AND STRATIFICATION. 79 



them to be floated beneath it to great distances, by a 

 succession of minute actions, till they finally settle 

 immoveably on the bottom. This very process may 

 be witnessed at the mouths of great aestuaries, as well 

 as in lakes. In the latter, as in the former, the 

 motions of the rivers first carry the materials forward 

 to certain distances proportioned to their power; and, 

 in the former, this action is incessantly renewed by 

 the daily motions of the tides ; in both, by the restless 

 state of the water. The distance to which mud is carried 

 into the ocean by the great rivers of America,, is very 

 great; and, to a less degree, the same phenomena are 

 visible on all sea coasts ; while the renewal or change of 

 place, in deposits of mud or sand, by the action of the 

 tides and by gales of wind, is familiar to every mariner. 



But this operation is also carried on in those 

 depths which our eyes cannot reach ; as is proved by 

 the sounding-line. Were the bottom of the sea not 

 covered with loose materials, soundings would every 

 where be clean and rocky; whereas mariners well 

 know that this is a very rare occurrence, and that it 

 exists only where elevated rocks are found ; forms on 

 which mud could not settle. That this state of the 

 bottom occurs all over the ocean, we cannot prove ; 

 as the depths of soundings are limited, and, owing to 

 the negligence of seamen, have been held far more so 

 than they actually are. But no soundings have ever 

 yet been made where mud and loose matters have not 

 been found, although at hundreds of miles from the 

 nearest land ; and in the trials, in Baffin's Bay, frag- 

 ments of limestone with calcareous mud were brought 

 up from depths of a thousand fathoms. 



Not only the deposition of loose materials, but the 

 separation of different kinds, is produced by water. 

 In lakes and aestuaries, this is witnessed in the 



