100 Kansas Academy of Science. 



grassy vegetation, aided by the washing influence of rain. 

 This opinion is practically substantiated (a) by the fact that 

 where rain is distributed somewhat generally throughout the 

 year little dust is formed; but where dry and wet seasons al- 

 ternate, as in central Asia and in the southwestern part of 

 the United States, vast quantities of dust may be moved dur- 

 ing the months of dry weather (Richthofen). When the dust 

 falls on bare dry ground, it is eventually swept away by the 

 wind, but where it settles down on ground covered with veg- 

 etation it is in a great measure protected from further trans- 

 port, and heightens the soil.'" 



Geikie again says, in substance f The origin of the loess is 

 a problem which has given rise to much discussion. It has 

 been regarded by some writers as the deposits of a vast series 

 of lakes; by others as a sediment washed over the surface of 

 the land by abundant rainfall; by others as deposits left by 

 swollen rivers discharged from the melting ice-fields. The 

 remarkable unstratified character of the loess as a whole, its 

 uniformity in fineness of grain, the general absence of coarse 

 fragments, except along the margins, where they might be 

 expected, its singular independence of the underlying contour 

 of the ground, and the almost total absence in it of fluviatile or 

 lacustrine shells, seem to prove conclusively that it cannot 

 have been laid down by rivers or eskars. On the other hand, 

 its internal composition, the thoroughly oxidized condition of 

 its ferruginous constituents, its distribution, and the striking 

 character of its enclosed organic remains, point to its having 

 been accumulated in the open air, probably in circumstances 

 similar to those which now prevail in the dry steppe regions 

 of the globe. It appears to mark some arid interval after the 

 height of the glacial period had passed away, when, whilst the 

 climate remained cold and the Arctic fauna had not entirely 

 retreated to the north, a series of grassy and dusty steppes 

 swept across the heart of Europe and America. 



As to the origin of the loess LeConte, in substance, says:' 

 Over large areas bordering the Mississippi and its tributaries, 

 and forming conspicuous bluffs of these rivers, there is found 



5. Geikie, Text-booli of Geology, p. 332. [This last theory is in accord with the 

 writer's observations in the soutli western part of the United States. The adobe clays 

 on top of the basalt northwest of Fort Apache, Ariz., are being added to year by year 



;by dust accumulation.] 



6. Loc. clt., p. 1060. 



7. Elements of Geology, p. 583. 



