Page:Popular Science Monthly Volume 72.djvu/507

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N the arid southwest parts of the United States, the crude water signs of the Indians have often pointed the white man to a spring. The government topographic maps covering sections of this region of sparse rainfall give the location of many springs. Throughout the longer-known and more-traveled desert areas of the world, the few oases have fixed the routes taken by caravans. Numerous books are available detailing facts that bear on the geographic influence of springs



 in which the altitudes were ascertained by working aneroids in pairs, a method explained in the Journal of Geology, Vol. XV. (1907), p. 492. In this area there are 203 dwellings, 148 of which are located at springs.