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THE POPULAR SCIENCE MONTHLY 



Fig. i. Expanse of Vast Dunes in Hueco Bolson ; the white sands of purest 

 gypsum are blown out of great desiccating salinas. 



tiling of the potency of wind-action in the general leveling and lowering 

 of the country. Of late years others who have traversed this field have 

 caught occasional glimpses of deflative activity. Spurr notes certain 

 minor aspects of it in the intermont basins of Nevada. Davis mentions 

 others in Utah and Arizona. Cross calls attention to some notable 

 phenomena in the San Juan district of southwestern Colorado that he 

 mainly ascribes to wind-action. Hill describes still other features in 

 northern Mexico. Free summarizes the liteiature on the action of the 

 wind in the formation of soils. In none of these records of observation 

 is the great principle of regional eolation recognized or even suggested. 

 Through all of them the influence of the idea of peneplanation by water 

 is overpowering. 



No phase of land-sculpturing by water explains the peculiarities of 

 desert relief. Where in humid lands are there such vast and even sur- 

 faces as the intermont plains of arid regions? Where under conditions 

 of moist climate do such lofty mountains stand out so isolated as in our 

 southwestern country — ideal monadnocks only theoretically and faintly 

 suggested elsewhere? Where but in a dry climate does entire absence 

 of foothills characterize the mountain ranges? Towering desert emi- 

 nences lise out of elimitable expanse of level plain as volcanic isles jut 

 from the sea. Plain meets mountain as sharply as the strand-line of 

 the ocean. The rock-floor of the desert is often a plain itself worn out 

 on the beveled edges of the strata beneath. The remarkable plateau- 

 plains clearly represent former plains-levels. The soil-mantle is gen- 



