THE NEBRASKA SAND HILLS. 275 



In the regions of widest valleys the ranges of hills often show a suc- 

 cession of higher hills as one passes back from the valley to the highest 

 points on the divide, Vvhich may be 300 feet above the level of the val- 

 ley. In the regions characterized by short valleys and basins the gen- 

 eral landscape is strikingly different because in such places the hills 

 rise on all sides without any regularity. Low hills, intermediate hills 

 and high hills are all closely associated, with no long separating valleys. 

 The result is' a very abruptly rolling surface with rounded or oblong 

 depressions of varying depth, with the rounded or conical dunes above. 

 There are places where this sort of topography stretches in all direc- 

 tions as far as one can see. 



As the name implies, the hills are composed of sand. This sand is 

 of a light straw color composed mostly of fine grained quartz. The 

 purest sand is found in the newest soil areas such as in "blow-outs" 

 or other places where the overlying vegetation has been completely 

 removed by the wind. In many places, notably in the river thickets and 

 in the numerous thickets scattered throughout the hills, there is a copi- 

 ous admixture of organic remains and so the surface soil in such places 

 is a rich black sandy loam and is very fertile. But the characteristicr 

 soil of the region as a whole is the pure dune sand composed of fine 

 particles. As to the chemical nature of the sand, the following table 

 shows it to be very high In insoluble mineral matter and very low in 

 soluble organic or inorganic plant-food materials. 



COMPOSITION OF SAND HILL SOIL' 



Insoluble matter 



Potash 



Soda 



Lime 



Iron oxide 



Alumina 



Phosphorus pentoxide 



Sulphur trioxide 



Water and organic matter 



Total 100.00 100.00 



The following table shows the size of the soil particles in per cent, 

 and the average of three detei'minations from different stations in the 

 Sand Hills: 



SIZE OF SOIL PARTICLES. 



Size in mm. 2.0-1.0 1.0-05 U.5)-0.'J.5 0.2.5-0 10 0.10 05 0.(J5-0.01 0.01-O005 0.005-<).0001 



Station 1 0.00 0.12 3.28 70.05 22.29 1.14 0.23 2.12 



Station 2 0.00 0.41 8.59 46.62 39.56 0.86 0.28 3.35 



Station 3 0.08 1.15 8.20 40.07 39.17 2.98 0.63 5.05 



Average of 3 stations. . 0.02 0.56 6.69 52.24 33.67 1.66 0.38 3.50 



* From a series of analyses by Dr. Samuel Avery, lOO.j. 



2 From Professor E. H. Barbour, Nebr. Geol. Survey, Vol. 1, 1903. 



