104 Kansas Academy of Science, 



show a bedded, laminated structure. Wind action alone can 

 account for its being such a compact substance as it is. 



"The multiple age of the loess is as easily accounted for, as 

 with the many climate changes attendant upon the periods of 

 the ice age, conditions may readily at different times have so 

 far favored the work of the wind as to have allowed the ac- 

 cumulation and the preservation of its sediments." 



Concerning the loess deposits of Montana, N. S. Shaler 

 says:" "The condition of the formation of this loess deposit 

 may be observed at any time when the earth is dry and the 

 wind is strong enough to lift the dust, as is the case for a con- 

 siderable part of the year. From the surface of the benches 

 of the valleys, as well as from the scantily vegetated lower 

 parts of the mountain ranges, dust ;g blown to and fro in 

 large quantities. So long as it encounters no closely set vege- 

 tation it does not come to rest. It is only when it finds its way 

 amid densely set plants in the limited areas watered by snow- 

 fed streams that it escapes from the controlling winds. In 

 such places it is quickly fixed, to remain so as long as the natu- 

 ral or artificial irrigation continues. The process of wind 

 erosion here, as elsewhere under like conditions, serves to pro- 

 duce and transport a great amount of fine detritus to the posi- 

 tion where it may be readily taken up by the rivers and sent 

 on its way to the sea. The result of this action is at once to 

 increase the efficiency of river work, and to overburden the 

 streams with fine sediment. Incidentally it serves to diminish 

 the down-cutting of the upper parts of a river system, the 

 parts just below the true torrents in which arid conditions 

 most occur, by overloading the waters with transporting ma- 

 terial. Thus, in an arid mountainous region there is an upper 

 zone of true torrent work, and below it a valley zone where the 

 erosion is of a very contrasted nature, being evenly and widely 

 distributed with and serial delivery of the detritus of the 

 streams." 



Concerning the loess of Minnesota, F. W. Sanderson, in sub- 

 stance, writes :'"' "The loess as a deposit in this region is never 

 more than a thin veneer, seen occasionally on the highest hills. 

 It is therefore scarcely a typical loess, since being near the 

 surface the humic acids have, from time to time, as it was laid 

 down, had ready access to it. It is a wind-borne dust that was 



11. Bull. Geol. Soc. Amer., vol. X, pp. 246, 247. 



12. Bull. Geol. Soc. Amer., vol. X, p. 349. 



