10 FOEESTATIOX, SAXD HILLS XEBEASKA AXD KAXSAS. 



tliose alono: the Cimarron also, have been formed br the breakinof 

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

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

 waters of the Arkansas Kiver. The mineral composition of these 

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

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

 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 roimded. there are present certain constituents 

 which are not foimd in the Xebraska sands and which give the 

 particles greater cohesion. The most important of these is probably 

 iron oxide. The Colorado sand, which is fomid in a few locahties m 

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

 either chemically or nnneraUy. but it has a shghtly larger percentage 

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



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

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

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

 '' active"' sand dunes, they have a rough topogi'aphy. whereas the 

 Kansas hills are low, and the topogi^aphy of that region may be 

 typified by the word ''rolling." 



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

 called the '''wet-valley region." the '^diy-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, m 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 vaUeys are sometimes 

 valuable for agriculture, and, especiahy ia the vicinity of the lakes, 

 make exceUent hay meadows. 



The dry-vahey region occupies the southern haK of the sand-hill 

 region and dift'ers from the wet-vahey region mahily ia having a 

 better soh drainage . which prevents the formation of lakes and ponds. 

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



At various places ^dtidn both the wet and dry valley regions there 

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

 that h'ing between the ^liddle Loup and Dismal Rivers. While the 

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

 northwest and east-southeast, as thi'oughout the region, here the 

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

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

 more frequently merely pockets. The midergroimd drainage is com- 



1 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 i)er cent, medium sand 12.2 per cent, fine sand 56.2 per cent, very fine sand 16.6 

 I)er cent, silt 1 per cent, clay 4.6 per cent. 



