THE 



POPULAR SCIENCE 



MONTHLY. 



MARCH, 1912 



GLIMPSES OF THE GREAT AMERICAN DESERT 



By Professor RAYMOND J. POOL 



THE DNIVEESITY OF NEBRASKA 



THOUSANDS of years ago when the forces of nature were at work 

 shifting and gradually shaping the features of the Great Plains, 

 large areas of Tertiary sandstones were exposed in Dakota, Wyoming, 

 Nebraska, Kansas and other parts of the western plains. As topo- 

 graphic features were slowly evolved, these sandstones, being young 

 and soft, readily yielded to the eroding action of the elements and were 

 reduced to light, fine-grained sand. In addition to this sand formed 

 in situ probably considerable amounts of other sands were washed or 

 blown into the region from farther west. Great quantities of the sand 

 thus formed were caught up by the wind and heaped into mounds that 

 finally grew to be large sand dunes extending in long ranges and ridges 

 for many miles over the sandstone beds. Thus were the Sand Hills of 

 the Great American Desert formed in the days preceding the advent of 

 plants or men into the regions now characterized by the billowy hills 

 covered with the bunch-grasses and their associates. 



The Sand Hill landscape in these early days was probably a restless 

 maze of wandering sand dunes. In later years certain plants crept in 

 from the surrounding plains, only to be uprooted and blown away. 

 After many such invasions some individuals finally succeeded in main- 

 taining a foothold in the more protected portions of the hills. Not- 

 withstanding the terrible conditions imposed by an arid climate and a 

 continually shifting soil, vegetation continued to spread to other areas 

 from these primary centers of establishment. 



Some time after the Sand Hill flora had gained a lasting hold upon 

 the dunes and the greenish hue of vegetation had spread over the great 

 expanse of hills, enormous herds of bison came charging into the region 



vol,. liXXX. — 15. 



