10 FORESTATION, SAND HILLS NEBRASKA AND KANSAS. 



those along the Cimarron also, have been formed by the breaking 

 down of the Tertiary grit found in the immediate vicinity, and also 

 by the weathering of the rocks on the mountain sides at the head- 

 waters of the Arkansas River. The mineral composition of these 

 dune sands shows them to be composed of quartz, feldspar, mica, iron 

 oxide, and other constituents which are characteristic of the local grit 

 and of the granites of the Rocky Mountains. While these sand dunes 

 are composed * of almost pure sand, medium or fine, and with parti- 

 cles more or less rounded, there are present certain constituents 

 which are not found in the Nebraska sands and which give the 

 particles greater cohesion. The most important of these is probably 

 iron oxide. The Colorado sand, which is found in a few localities in 

 the Kansas sand hills, is very little different from the dune sand 

 either chemically or minerally, but it has a slightly larger percentage 

 of very fine sand and silt, and hence coheres more strongly. 



While the Kansas sand hills are, because of the greater amount of 

 silt, compact and now almost perfectly stable, the Nebraska sand 

 hills are still being moved, in many instances by the wind. Like all 

 "active" sand dunes, they have a rough topography, whereas the 

 Kansas hills are low, and the topography of that region may be 

 typified by the word "rolling." 



The Nebraska sand hills may be divided into three regions, to be 

 called the "wet-valley region," the "dry-valley region," and the 

 "choppy hill region." The wet-valley region is, generally speaking, 

 the northern portion of the hills and is typified by long valleys with 

 an easterly and westerly bearing, in the east end of which there are 

 usually one or two small bodies of water. These bodies of water 

 vary greatly in size from year to year. The valleys are sometimes 

 valuable for agriculture, and, especially in the vicinity of the lakes, 

 make excellent hay meadows. 



The dry-valley region occupies the southern half of the sand-hill 

 region and differs from the wet-valley region mainly in having a 

 better soil drainage, which prevents the formation of lakes and ponds. 

 The topography is more rugged, and the hills are higher. 



At various places within both the wet and dry valley regions there 

 are found areas of choppy hills, one of the largest of such areas being 

 that lying between the Middle Loup and Dismal Rivers. While the 

 general trend of the ridges and valleys in these localities is west- 

 northwest and east-southeast, as throughout the region, here the 

 ridges are short and frequently broken by round-topped hills, while 

 the valleys are seldom more than a quarter of a mile long and are 

 more frequently merely pockets. The underground drainage is com- 



i Six miles south of Garden City dune sand was found to be made up in the following proportions : Grave 

 1.1 per cent, coarse sand 8 per cent, medium sand 12.2 per cent, fine sand 56.2 per cent, very fine sand 16.6 

 per cent, silt 1 per cent, clay 4.6 per cent. 



