53 6 THE POPULAR SCIENCE MONTHLY. 



have any appreciable, to say nothing of a considerable, effect on 

 the climate. Even in irrigated countries only a barely perceptible 

 increase in the rainfall has been discovered. In Spain, France,, 

 and Italy, irrigation is now not only required for farming, but it 

 is more widely practiced than ever before ; yet, if the " rain-belt " 

 theory were correct, these countries would long ago have had 

 sufficient precipitation for successful agriculture. There is. 

 scarcely any rainfall in the valley of the Nile to-day, after centu- 

 ries of cultivation and of annual floods. 



Our " plains," or arid region, lie east of the Rocky Mountains, 

 and are at least four hundred miles across. Although the pre- 

 cipitation gradually decreases as one proceeds westward from the 

 Missouri River, it is difficult to fix an isohyetal line. But the line 

 is somewhere between one hundred and two hundred miles west 

 of the Missouri, as the flora clearly shows. It seems to have been 

 taken for granted that the plains were treeless and well-nigh 

 grassless because of lack of rain. Whether the absence of trees 

 is ascribable to the pulverulence of their soil, or the germless 

 lacustrine deposit which covers them, or the excess of moisture,. 

 or the fires of the Indians, it is clear that it is not due to rain- 

 lessness, because the dry hill-tops in the midst of the arid region 

 have some trees. In other words, there is no evidence whatever 

 that the precipitation on the plains to-day is any greater than it 

 was fifty or one hundred years ago ; and there is every reason to 

 believe that it is less. 



But, it is said, the observations west of the Missouri show a 

 material increase in the rainfall. This is not true. In the reports 

 of the Kansas State University and the Kansas State Agricult- 

 ural College we learn that the rainfall for the ten years from 

 1879 to 1888 is not so great as that of the previous decade. One 

 authority on the subject has recently taken, among other series, 

 the observations at Fort Leavenworth from 1837 to 1883, and,, 

 testing by the proper mathematical processes their variabilities 

 and probabilities, demonstrates that there is no indication what- 

 ever of permanent climatic change. Yet Fort Leavenworth is 

 one hundred and fifty miles east of the eastern line of the dry 

 region. 



It must appear irrational to any one, after a moment's reflec- 

 tion, that the settlement of five or six thousand people in a county 

 usually twenty-four by thirty-six miles in dimensions, and the 

 tillage of a small part of its area, would so materially increase the 

 rainfall in the brief period of ten or twenty years as to make agri- 

 culture successful and profitable where before it was not possible. 

 Extending these limits to the wide expanse of States does not 

 make the idea any more tenable. Yet on such conditions as these 

 the theory as applied to our plains is based. The reports of 



