RIVER DEVELOPMENT 



177 



into the ground. Pools and lakes are formed in the in- 

 closed basins? and sluggish streams with irregular little 

 crooks, which show that the streams have hardly decided 

 where they want to go, wander in the slight depressions 



NIAGARA FALLS 



down the gentle slopes and unite with other streams 

 here and there until a river of ever increasing size is 

 formed. 



In some places the streams flow through lakes where 

 they deposit their sediment, thus filling the lake basins. 

 Here and there they pass over hard layers of rock which 



