Page:Popular Science Monthly Volume 42.djvu/620

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600
THE POPULAR SCIENCE MONTHLY.

lands. Large sums of money have also been wasted in vainly bombarding the skies for rain, contrary to every known law of Nature. The Department of Agriculture has investigated the underground waters of the Great Plains region east of the Rocky Mountains, but the underground supply of the true American Desert lying between the Rockies and the Sierras has been little studied.

 
PSM V42 D620 Prevalent conception of ordinary artesian conditions.jpg
Fig. 1—Prevalent Conception of Ordinary Artesian Conditions.Drawn from a geological report.
 

This section includes one fifth the total area of the United States and most of the great central plateau of Mexico. It is marked by peculiar geographic, geologic, and climatic phenomena altogether different from those of the rest of the country, chief of which is the absence of surface water. Streams are rare even in the mountains, and, with the exception of the Colorado, the Snake, and the Rio Grande, not a drop of its surface water reaches the sea, so great is, the evaporation and the capacity of the porous desert soils for absorption. Almost any Eastern State has a greater area of surface water than has all the arid region; and the smallest New England brook, could it be transported West, would be a great blessing. In this arid section there are many thousand square miles without a drop of water even for drinking purposes. Nearly every available stream has been appropriated for irrigation by the present population, and all improvement in the water supply must come from underground sources.

It is wrong to encourage anticipations of enormous supplies of underground water where rainfall is so slight; but when we remember that in this region water is of greater value than land, or rather that land is worthless without water, the procurement of even small supplies, sufficient for stock, for irrigating small areas, or for supplying the thirsty locomotive, will be of great value. In view of these facts it is well to understand the laws of the occurrence