680 J. A. UDDEN COMPOSITION OF CLASTIC SEDIMENTS 



compared with the other analyses, the range of variation in the coarse- 

 ness of the sand dne to differences in the velocity of the wind. Evidently 

 this is not very great. 



At Folly's Cove, in Massachnsetts, some beach sand is driven inland 

 by the winds. The absence of fine particles in this sand is no doubt 

 partly dne to washing on the beach. 



Some sand has been collected from small and freshly formed drifts on 

 plowed fields and on the open prairie in the eastern part of North Da- 

 kota. The rather large amount of dust in all of these analyses is evi- 

 dently due to the fact that the wind has just begun its work on surface 

 deposits, which contain hne materials in some abundance. 



Scattered dunes occur in the basin of the Green River, in Illinois. 

 Though the superficial deposits here are but little affected by the action 

 of the atmosphere now, the topography of several sandy belts in this val- 

 ley indicates earlier deflation by the atmosphere. The sand is moderately 

 well sorted. 



Some years ago a drift of sand was blown up in a field near Lindsborg, 

 Kansas. The soil in this place was composed of a sandy alluvium, which 

 held very little fine material. No specially noteworthy feature appears 

 in the mechanical composition of this sand. 



The most extensive sand-hill region in the United States is probably 

 found in the western part of Nebraska. Here the winds have been at 

 work for a long time rearranging, shifting, and sifting extensive beds, 

 which were formed in Pliocene and early Pleistocene time. Entire 

 counties are covered by extensive ranges of sand hills, sometimes exceed- 

 ing 300 feet in height. The bulk of the blown sand in this region largely 

 exceeds that of any other locality from which any material has been col- 

 lected. The lag gravels are conspicuously absent in the samples exam- 

 ined, nor do these contain more than a trifle of dust. It is the most 

 uniformly sorted of all the sands described. Two of the samples were 

 selected to represent the extremes of variation among a series of layers 

 which were seen in an exposure with well defined bedding. One was 

 taken from the coarsest seam which could be seen and the other from the 

 finest. The difference in texture was quite apparent to the eye, as the 

 seams appeared in the natural exposure, but it seems rather insignificant 

 in the analyses. 



South of Moline, Illinois, there are some drifts of sand in a remnant 

 of an old terrace. This blown sand has not been carried farther than 

 two or three hundred yards. 



In the southern part of Henderson County, in Illinois, there is a 

 range of sand hills which follows the bluffs of the Mississippi River. In 



