Page:Popular Science Monthly Volume 80.djvu/214

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THE POPULAR SCIENCE MONTHLY
PSM V80 D214 Shaded areas indicate the sand hill areas.png
The Sand Hill Areas are indicated by the Shaded Portions on the Map.

in quest of forage. The vegetation was closely grazed and tramped into the unstable soil. And then the red man came, who killed the bison for food, clothing and for many other useful purposes. He sought to improve the range for the wild beast and for his own stock by burning the grass at certain seasons of the year. In this way a third and still greater menace was forced upon the plants that were struggling so hard to cover the Sand Hills with a permanent mantle of vegetation.

The Sand Hill region of Nebraska is one of the largest and best known portions of the sand hills of the Great Plains. In. our state the main body of Sand Hills is oblong in shape with irregular margins. This region lies north and west of the central portion of the state. On the northern edge of the region there are numerous deep canyons with steep, more or less wooded sides. A few more or less isolated areas of Sand Hills occur outside this great main region both north and south of the Platte. A glance at the accompanying map will show the location and comparative size of the main region and the outlying areas of sand hills.

The Sand Hills of Nebraska cover an area of more than 18,000 square miles, almost one fourth of the total area of the state. This is about equal to the combined areas of New Hampshire and Vermont. The hills are all round-topped or conical and smooth, clearly showing that they had been shaped by the wind long before their invasion by plants. There are many depressions between the hills, many of which assume the proportions of valleys more than a mile in width and sometimes many miles in length. From these well-developed valleys the low places decrease in both width and length until they are mere narrow, saucer-shaped basins or "pockets" a few hundred yards across. The well-pronounced valleys are, as a rule, about parallel and trend in a general southeast and northwest direction. Such valleys are frequently completely inclosed by ranges of hills and in this way effectively separated from adjacent valleys, though such may not be more than a half