174 THE WORK OF RUNNING WATER 



Depressions that are very shallow and are largely filled 

 with vegetable growths are called swamps. 



The Power of Running Water. Eunning water has the 

 power of carrying solid materials. If it is moving slowly, 

 this power is not great; if moving swiftly and in great 

 volume, it is tremendous. The carrying power of a stream 



LAKE DRUMMOND 



A lake in Dismal Swamp, Virginia, which is being filled by vegetable 

 growth. 



increases very rapidly if its velocity is increased. A stream 

 having its velocity doubled will carry several times as 

 much material as before. Thus it happens that water 

 running over a surface sweeps loose material with it, the 

 amount varying with the rapidity and volume of the flow- 

 ing water. 



As this loose material sweeps over solid surfaces, it cuts 

 them down. Thus flowing water is continually wearing 



