308 



GENERAL SCIENCE 



gravel it carries is rapidly deepening its channel, while 

 the lofty sides of its canon are little changed by ages of 

 weathering. 



The St. Lawrence River carries practically no sediment 

 of any sort and so erodes its course very slowly. 



Deposition. Deposition, like erosion, depends very 

 largely upon the slope of the river bed and the velocity of 



FIG. 264. The Delaware River above Water Gap, Pa. 



The deposition of materials in the bed of the river will extend to form 



broad, open plains. 



the current. The materials carried or rolled along by 

 rivers are deposited at various points in their channels or 

 carried to the sea (Figure 264). The finer portions of 

 silt may reach the ocean, where it is deposited over the 

 ocean floor or in huge delta bars at the mouth of the river, 

 as in the case of the Mississippi River or the Nile River 

 (Figures 265, 266). The fine sand is deposited along the 

 lower portion of a river's course. As we go up the river 

 the deposit becomes coarser, until in the upper part of its 

 course we find stones of considerable size. 



