Studies for Students. 



EROSION, TRANSPORTATION, AND SEDIMENTATION 

 PERFORMED BY THE ATMOSPHERE. 



In dynamical geology there is one line of inquiry which has 

 received, comparatively speaking, but little attention from Ameri- 

 can geologists. Our text-books discuss in a thorough manner 

 the work performed by water, and they also tell us much about 

 the work of earthquakes, of volcanoes, and of glaciers. Some 

 of these phenomena appear so striking as always to challenge 

 our attention. Others are so common in their occurrence and so 

 obvious that they suggest themselves to our study and to our 

 reflection everywhere. The work performed by the winds in 

 the atmosphere appears hardly to have received its due share of 

 attention. The transportation of solid materials by the air is 

 one of those subtle operations in nature, which are apt to escape 

 our observation. The process is of an unobstrusive nature, and 

 only in certain localities becomes at all obvious. There are, 

 however, some scientists who have understood and urged the 

 great importance and efficacy of aerial transportation in geologi- 

 cal dynamics. Ehrenberg, Von Richthofen and Pumpelly will be 

 remembered first in this connection. Blake, Gilbert, Hayden, 

 N. H. Winchell, Chamberlin, Merrill, and others have described 

 instances of erosion and transportation by the atmosphere. But 

 it will be conceded, I think, that the subject has not received 

 any general and searching attention from geological students in 

 this country. This is the only excuse for presenting at this 

 time a few considerations bearing on the topic. I take the lib- 

 erty to state in a dogmatic way what appear to me to be some 

 laws governing aerial erosion, transportation and sedimentation 

 in general. It is not claimed that these statements contain 

 much that is new in substance. 



As ati agejit of erosioji air is far less efficie?it than water. 



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