148 Trans. Acad. Sci. of St. Louis. 



rather than real. Only the crust of the earth is com- 

 monly considered; and the analysis of most meteoritic 

 materials do not often show the true proportions of stony 

 matter. 



On the theory of meteoritic agglomeration the original 

 and often the immediate source of ore materials cannot 

 be so largely magmatic as it is vadose in nature. Quali- 

 fied in some ways and somewhat strengthened in others, 

 the general arguments of Forschaminer, Sandberger, 

 Winslow, Van Hise and Bain assume a new interest and 

 an added value. The main shortcoming, if such it be, is 

 merely in ascribing a role or principal origin of the ore 

 materials to rock-weathering, when a somewhat broader 

 interpretation of the facts and conditions seems neces- 

 sary. 



The manner by which metallic substances of meteoritic 

 origin may become incorporated with ore materials gen- 

 erally is not an intricate one. After reaching the surface 

 of the earth all cosmic dust and fragments must mingle 

 with the soil, more or less quickly oxidize, and enter 

 through means of the circulating ground-waters or other- 

 wise sooner or later reach the deep-seated zone, in the 

 same way as any of the heavier mineral particles liber- 

 ated from the surface rocks through decomposition are 

 supposed to do. The processes involved are essentially 

 the same as for the changes and movements of rock-form- 

 ing materials generally. The distinction to be made is 

 merely that instead of all of the ore materials being de- 

 rived from the breaking down of rocks of the lithosphere 

 a very large proportion is regarded as coming from extra- 

 terrestrial sources. 



In the course of the inward migration of ore materials 

 temporary ore-bodies are often localized in the vadose 

 zone, and even lower down. How much of these mater- 

 ials is of recent extra-terrestrial origin and what propor- 

 tion is really a product of rock decay is at the present- 

 moment difficult to estimate. Even dominant notions 

 concerning ore-bodies seemingly directly associated with 



