THE WORK OF STREAMS 



129 



formed, so that bare rock is always exposed, the work of 

 ground water and of plants and animals is reduced greatly. 

 It consequently follows that, other things equal, weathering 



FIG. 120. Weathered forms in granite, Laramie Hills, Wyo. Three sets 

 of joints may be seen, and their influence upon the weathering of the 

 rock is clearly evident. 



proceeds most rapidly when its products are rather promptly, 

 but only partially, removed. 



The fact that over most of the surface of the land there 

 is a mantle of soil and subsoil indicates that, in general, 

 weathering exceeds transportation. 



Questions 



1. Does the absence of soil in any given place mean that weather- 

 ing is not in progress there ? 



2. What are the principal agents of weathering in the Sahara? 

 New York ? Louisiana ? The Amazon Valley ? 



3. Would a given stone wall stand longer in Labrador or in 

 Florida ? What are the principal agents of weathering by which 

 it would be destroyed ultimately in each place ? 



4. What differences in weathering might reasonably be expected 

 on the two sides of an east and west valley ? On the two sides of a 

 high north and south mountain range in the latitude of the United 

 States ? Of an east and west range ? 



