WATER AS A MECHANICAL AGENT. 



201 



at the outlet where the stream resumes its relatively rapid flow. The final 

 result when reached is the conversion of the bed of a lake into a river 

 channel. 



185. 



Map of the Great Lakes. L. Y. Schermerhorn, '87. 



The smaller lakes are very feeble workers, and hence, owing to gentle 

 trituration by the little waves, the shores are often muddy. Theoretically 



186. 



Longitudinal sections of the lakes on the line of deepest water. Schermerhorn, '87. 



V 



the waters of the lakes over high plateaus, like those of the head waters of the 

 Mississippi, have great energy ; but they usually lie without a chance to 



