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ELIOT BLACKW ELDER 



and would almost surely succeed if they persisted so long as to 

 planate the surroundings. 



It seems to be established that prolonged wind abrasion in 

 deserts does produce plains on which only scattered elevations 

 remain; although the criteria for recognizing ancient wind-made 

 plains are hardly as well agreed upon by physiographers as are 

 the criteria for peneplains. Such a plain, if undefaced, should have 

 certain characteristic features which could be used in recognizing 

 its origin. Its depressions should be broad, relatively flat-bottomed 



Fig. 14. — Photograph of mountain (11,500 feet) near Gypsum Creek. 

 Paleozoic limestones trunkated at summit. 



Tilted 



hollows, rather than graded valleys, and these hollows should have 

 a definite relation to the weakest rocks. Wherever hard and soft 

 rocks are exposed there should be the characteristic wind-etched 

 ridges, ledges, mushroom rocks, etc. The pebbles in the gravel 

 strewn upon the flats by occasional floods should be pitted, pol- 

 ished, and even beveled by the sand-blast. Only the most massive 

 and resistant bodies of rock should stand out as hills and mountains. 

 Unfortunately it is almost impossible to apply the test of these 

 criteria to the Wind River plateau in its present condition. The 

 details of its surface forms and material have been greatly modified 

 by the long-continued action of frost above timber-line. The 



