20 



AGRICULTURE. 



(8) Snowslides. — On the mountain sides 

 great masses of snow which have accumulated 

 through the winter become loosened bv water, 

 as in the case of the landslide, and are drawn 

 down the slope with great momentum, carrying 



FIG. 5. — SHALES "creeping" UNDER THE ACTION OF 

 FROST. (U. S. G. S.) 



boulders, vegetation, everything within their 

 path, and literally scraping the solid rock bare. 

 (9) Glaciers. — It is now well established that 

 in both North America and Europe glaciers, 

 or great sheets of moving ice, existed in com- 



