DUIKTIN<i SAND. 15 



maximum ingredient. Had it been taken a little deeper, 

 it would have been more like the rest, for the coarser 

 grains are least easily dislodg'ed from this (•x])osed posi- 

 tion and remain, while the finer sand is blown away. 

 Some coarse dust is still mixed in the sand at this place 

 in one instance (no. 24). All taken together and com- 

 pared with sand from other places, these samples may be 

 said to be imperfectly sorted, owing no doubt to the 

 recency of the inception of the wind action in this locality. 

 The dunes on the south-east shore of Lake Michigan 

 have furnished the materials for six analyses (Tab. IV). 

 These sand hills havfe been recently formed and are lai'gely 

 made up of sand that is freshlj^ supplied by present wave 

 action on the shore of the lake. In this place also the 

 coarse grades occur with the typical dune sand in small 

 quantities on the veiy top and front slope of the hills 

 (see nos. 25, 26, and 28). But there is practically no 

 coarse dust to be seen, presumabh^ because no such fine 

 material is present in the beach sand. This locality and 

 the previous are the only ones that furnish instances of 

 dune sand having a second maximum in the coarser 

 grades (no. 21 and 28). 



The bluffs facing the bottom lands of the Mississippi, 

 east of Cordova in Illinois, are here and there being eroded 

 by the northwest winds. 8ome sand taken from a small 

 drift only a foot in height exhibits imperfect sorting like 

 that observed in the sand fi-om New Boston and Michigan 

 City (Tab. V). 



In Rice county in the central part of Kansas there is a 

 tract of sand hills extending many miles along the little 

 Arkansas river. These are derived from underlying late 



