The Behavior of Rivers 37 



begin and grow do they also grow old? It is said any fool can 

 ask questions but only the wise can answer. Geologically all 

 these questions may be answered, and no more "wisdom v is 

 required than that of common sense and a study of what is 

 going on all about us, almost within our own back yard. 



How Does a River Begin? 



Imagine a land surface having a uniform slope to be lifted 

 above the sea. It has been stated that all lands that are above 

 sea level are being worn and eroded, and that the particles of 

 rock tend to be carried to the sea. (All earth materials in a 

 general sense are rock.) If rains fall and winds blow and heat 

 follows cold then the land will be eroded and streams will tend 

 to be developed. For simplicity let the new land area be 

 thought of as a continent. Where will a river begin? Let the 

 rains descend and the winds blow. The first water to reach 

 the sea from the land will be that which fell nearest the edge 

 of the land. Then the next water to reach the sea will be that 

 which fell next beyond inland. This will be granted without 

 much "wisdom." Then it must follow that the next water to 

 reach the sea will be that which fell a little farther inland. 

 Then the water that fell at the center of the new continent will 

 be the last to reach the sea. Running water erodes the land, 

 hence some particles of rock will be carried to the sea by the 

 waters that first reached the sea, and so the waters that fell next 

 inland will have the benefit of the eroded channel made by the 

 waters that have already gone. So, farther and farther inland, 

 the waters will take advantage of the channel eroded by the 

 waters that have gone before. The waters from each succes- 

 sive area will erode as they go, and so there will be more and 

 more erosion nearer the shore or edge of the land surface, and 

 less and less farther from the shore, and the new valley will have 

 less and less width and depth toward the center of the land. If 

 we imagine the soil (or rock) of the new continent to be some- 

 what heterogeneous in composition (and most soils are) then 



