IOWA ACADEMY OF SCIENCES. 87 



The strong northwesterly winds blowing over the prairies, 

 which during a part of the year at least were quite dry, gath- 

 ered up clouds of sand and dust. The coarser material was 

 blown and rolled about on the surface, the constant grinding 

 furnishing renewed supplies of finer material, while this finer 

 material was carried higher, being finally swept over the for- 

 ests, and there deposited.^* 



That this is not a fanciful view of the work actually per- 

 formed by winds has been nicely demonstrated in eastern Iowa 

 during the past two years. High winds prevailed during con- 

 siderable portions of both years, the dry spring of 1895 being 

 particularly remarkable in this respect, and observations upon 

 the material so transported were made in Johnson county. In 

 the northern prairie portion of the county, beyond Solon, fine 

 sand was heaped up m open places, in some cases to a depth of 

 over a foot, within twenty -four hours, while fine dust only was 

 carried into adjacent groves, and was there deposited upon 

 every available surface to a depth of not less than one mm- 

 The writer's observations of the effect of the winds which so 

 prevail in Nebraska also confirm this. 



That this fine material now constituting the loess, was so 

 deposited in forests is further shown by its distribution. That 

 the loess and the original forest area in eastern Iowa alaiost 

 exactly coincide is a well established fact, which has been 

 demonstrated beyond question by MsG-ea.^' 



The forests are found along the streams, and also principally 

 on the southern and eastern slopes of the hills, and the loess is 

 found in exactly the same situations. 



Indeed it has often been suggested that there is something 

 peculiar to the loess which renders it favorable to the develop- 

 ment of the forests — whereas the fact seems to be that the 

 forest is especially favorable to the deposition of the loess if 

 lying adjacent to or near drift-covered plains. 



That the forest could have preceded the loess is shown by 

 the fact that scrub growths of bur oaks have been able to gain 

 a foothold along the shores of some of our northern (Iowa) 

 lakes and streams in a purely glacial soil, thus forming the 

 nucleus of a forest in comparatively recent time, while in the 

 same region in groves evidently somewhat older a thin layer 



14 Interesting observations were made in 1894 by F. H. King (see Eleventh An Rcrt of 

 the )ri)<c(msin Aur. Ex. Sta., p. 292 ct scq.) upon the effect of winds on vegetation in drift- 

 ing soil wliicli bear out the conclusions presented in this paper. ■ 



isu. S. Geol, Sur., 11th Ann. Rep., Part I, pp. 296, et seq. 



