LESSON XLVI. 49 
This is a picture of an overflow of the Mississippi 
River. Look at your map of the United States, 
and observe that the greater part of our country is 
drained by that river; that is, the rain that falls in 
the States between the Allegheny and Rocky Moun- 
tains, runs into rivers which flow directly-or indi- 
rectly into the Mississippi. This is caused by the 
land sloping downward from these two chains of 
Mountains where the land is highest, to the Missis- 
Sippi River where it is lowest. 
To prevent inundations or freshets. which do great 
damage to houses, farms, ©. *. he people have 
raised banks, ca!lcd LEwnse yiver,