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,®® Pasarge,*° 
Spurr,** Cross** and others.*® 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 
* Abhdl. K. Sachische Gesell. d. Wissenschaften, 16. 1901. 
* Zeitschrift d. deut. geol. Gesell. 56:193. 1904. 
* Prof. Pap. U. S. Geol. Surv. 42:110. 1907. 
* Bull. Geol. Soc. Amer. 19:53-62. 1908. 
® Ibid. 19:63. 1908. 
