WATER, AND ITS USES 49 



the volume of its waters depend ? For how long a time will 

 this stream naturally continue to flow? 



4. To what distances up and down have you followed the 

 stream ? Which is the right bank (a) of this stream ; (b) 

 of any stream ? Describe in a general way the character of 

 country through which it flows, whether hilly, level, broken, 

 or mountainous. Recall any relation between the char- 

 acter of the banks of the stream and the rate of its 

 current. What differences exist in the bed of the stream 

 at different places? How are these accounted for? What 

 explanation is there for any swift and broken current 

 ("rapids")? What significance have places of compara- 

 tively still water ? What is true of the widths of the stream 

 at different points? What relation has this to the depths 

 at such places ? 



5. Of how much use in navigation is the stream? Why 

 so? Has it any use for manufacturing? Why? Name 

 other respects in which it is of use. 



VALLEY FORMATION, AND SURFACE EROSION 



1. From observations you have made of some gentle 

 slope (by field, roadside, railway cut, or earth pile) where 

 the earth is bare and subject to wash by rains, state what 

 relation is apparent between steepness of slope and (a) 

 crookedness of the channels cut by the "flowing surface 

 waters ; (b) depths of the cuts ? Offer an explanation (a) of 

 the crooks and turns in these channels ; (6) of the greater 

 depths of some cuts than others. What is meant by erosion 

 (e-ro'zhun) of soils? 



