50 LABORATORY LESSONS IN GENERAL SCIENCE 



2. Distinguish between a main channel, and its trib- 

 utaries. Why should there be any tributaries? What is 

 meant by a divide between adjacent channels ? 



3. Make a sketch of some imaginary stream and its 

 tributaries, and by appropriate lettering locate thereon 

 (a) the main channel; (6) a tributary; (c) the mouth of 

 the main stream ; (d) its source ; (e) a divide between two 



FIG. 20. Canyon of the Colorado River. 



tributaries. Inclose by a continuous dotted line on the 

 sketch what is included in the "water-shed" of the system. 

 What is the meaning of (a) river basin; (6) river system? 



