222 BOULDER REVERIES. 



prominent group so characteristic of the desert 

 plains of the distant West. The roots of this 

 vegetation form a network about the sand grains 

 and prevent the leveling of the dunes. 



In time, however, a tree is uprooted, or a for- 

 est fire burns off the vegetation. The protecting 

 network of rootlets is destroyed. A bare spot 

 results, over which the winds freely play. A 

 great storm from the north or northwest scoops 

 out a small bowl-shaped cavity and, carrying 

 the sand either south or southeastward, drops 

 it over the hillside. The cavity is cut deeper 

 and wider by succeeding storms, and a great 

 "blow-out" in time results. Where a few years 

 before stood a high hill or unbroken ridge, now 

 exists a valley, or cavity in the hillside, acres, 

 perhaps, in extent, and reaching nearly to the 

 level of the lake. The sands which were once 

 there now constitute new hills or ridges, which 

 have traveled, as it were, a greater distance in- 

 land. In many places the drifting sands have 

 wholly or partly covered a tall pine or oak tree. 

 Where but partly covered, its dead though 

 sometimes living top projects for a few feet 



