Keyes — Meteorites on the Painted Desert. 143 



Black Coloration of Desert Rock Surfaces. For other 

 reasons also, meteoric masses might not be easy to rec- 

 ognize among the rock fragments of the pebble pave- 

 ments, or on the gravel-strewn plains. The majority of 

 the more basic rocks of the desert are susceptible to 

 notable discoloration and wind-polishing. Until the 

 pebbles are broken in two they give little suggestion of 

 the real lithologic character. The only clew in such 

 cases to meteoric material is sometimes the greenish tint 

 of certain pebbles, that is caused by a slight hydration 

 of the nickel content. 



In arid regions the more basic iron-bearing rocks are 

 almost invariably coated with a black iron and manganese 

 film which, after being thoroughly polished by the wind- 

 blown dusts and sands, imparts every appearance of the 

 masses having been fused on the surface. In general 

 aspect it is not very unlike the surfaces of recently fallen 

 meteorites in moist lands. Among such dark laquered 

 rock-fragments it would be with the greatest difficulty 

 that true meteorites could be distinguished. That meteor- 

 ites do actually occur abundantly under such conditions 

 is now widely known among dwellers of the desert; and 

 that they will be more generally detected when especially 

 sought after is more than probable. 



Exportation of Finer Rock-Waste. The general phases 

 of erosion of desert regions by the winds are fully de- 

 scribed in the recent writings of Walther, 35 Pasarge, 36 

 Spurr, 37 Cross 38 and others. 39 Its bearing upon the dis- 

 closure of meteoric falls should be here emphasized. The 

 movement of desert soils and sands is to be regarded as 

 much more than a mere idle shifting of dry particles as 

 is commonly inferred. Besides the constant sweeping 

 back and forth of the soils and sands over the surface of 



35 Abhdl. K. Sachische Gesell. d. Wissenschaften, 16. 1901. 

 36 Zeitschrift d. deut. geol. Gesell. 56:193. 1904. 

 "Prof. Pap. U. S. Geol. Surv. 42:110. 1907. 

 38 Bull. Geol. Soc. Amer. 19:53-62. 1908. 

 89 JfeieZ. 19:63. 1908. 



