WIND DEPOSITS 



68B 



been lifted a little higher, and that is the reason why they have been 

 carried a little farther; but the difference is very slight, and consists 

 merely in a change in the proportions of the percentages on either side 

 of the maximum. 



Four series of wind sediments have been taken from successively more 

 distant points in front of dunes and sand drifts in Kansas, Illinois, and 

 North Dakota. The analyses of these series show that the grains which 

 approximate nearest to the dune sand in size are not carried very far. 

 The samples from Eice County, in Kansas, and those taken near Moline, 

 in Illinois, exhibit merely a decrease of the coarse admixtures and a cor- 

 responding increase in the fine admixtures for increasing distances 

 within a range of 200 feet. In distances less than 200 feet the percent- 

 ages of the fine ingredients increase from eight in the dune sand to 41 

 in the lee sand. 



A series of samples taken in front of the sand drift at Lindsborg 

 changes more rapidly, so that only 50 feet away 65 parts in a hundred 

 consist of very fine sand. The dune at this place was much lower than 

 the other, and this partly accounts for the rapid settling of the fine sand, 

 which here had a very short distance to fall. 



List of Samples in Tahle 25 



254. From the lee of sand dunes, Rice County, Kansas. 



255. From 6 feet in front of the lee drift of a dune. Rice County, Kansas. 



256. From 15 feet in front of the lee drift of a dune. Rice County, Kansas. 



257. From 24 feet in front of the lee drift of a dune, Rice County, Kansas. 



258. From a small lee drift, Lindsborg, Kansas. 



259. Ten feet in front of a small lee drift, Lindsborg, Kansas. 



260. Fifty feet in front of a small lee drift, Lindsborg, Kansas. 



261. Ten feet in front of a small dune near Moline, Illinois. 



262. One hundred feet in front of a small dune near Moline, Illinois. 



263. One hundred and sixty feet in front of a small dune, Moline, Illinois. 



Dust — General discussion. — To determine the size of the particles 

 that may readily be transported long distances by ordinary winds, we 

 should examine the nature of the loads which these winds generally 

 carry. I have collected a number of samples of such dust by different 

 methods, under different conditions of deposition and from different 

 localities. 



Miscellaneous collections of dust. — Some of the »dust samples collected 

 for this study are sediments which have been carried by the atmosphere 

 under more than ordinarily favorable circumstances and in currents of 

 more than ordinary strength. Such is sand and dust stirred up from the 



