OURNEYING seaward, 

 the water that finds 

 no basins to retain it, 

 forms streams. Ac- 

 cording as these differ 

 in size we call them 

 rivers, creeks, brooks, 

 and rills. These dif- 

 fer as do lakes in the 

 dissolved contents of their waters, according to the 

 nature of the soils they drain. Streams differ most 

 from the lakes in that their waters are ever moving in 

 one direction, and ever carrying more or less of a load 

 of silt. From the geologist's point of view the work of 

 rivers is the transportation of the substance of the 

 uplands into the seas. It is an eternal levelling process. 

 It is well advanced toward completion in the broad 

 flood plains of the larger continental streams (see map 

 on page 63) ; but only well begun where brooks and 

 rills are invading the high hills, where the waters seek 

 outlets in all directions, and where every slope is 

 intersected with a maze of channels. The rapidity of 

 the grading work depends chiefly upon climate and rain- 

 fall, on topography and altitude and on the character 

 of the rocks and soil. 



77 



