IOWA ACADEMY OF SCIENCE 
175 
is considered ; and the analysis of meteoric material does not often show 
the true proportion of stony matter. 
The introduction of meteoritic materials into rock-masses and their 
incorporation into ore-bodies are not intricate processes. On- the theory 
of meteoritic agglomeration the original and often the immediate source 
of ore materials cannot be in nature so largely magmatic as it is vadose. 
Qualified in some ways and strengthened in others, the general argu- 
ments of Forchhammer, Sandberger, Winslow, Van Hise, and Bain 
assume a new interest and an added value. The main shortcoming, if 
such it really be, is merely in ascribing a sole, or principal, origin of the 
ore materials to rock-weathering, when a somewhat broader interoretation 
of the facts seems necessary. 
It is not difficult to fancy the manner in which metallic substances 
of meteoritic origin. may become incorporated with ore materials gener- 
ally. After reaching the surface of the earth, both cosmic dust and the 
larger meteorites must mingle with the soil, more or less quickly oxydize, 
and enter by means of circulating groundwaters or otherwise, the deep- 
seated zone, in the same way as any of the heavier mineral particles lib- 
erated 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-forming ore-materials. The distinction to be made is 
that instead of the ore material being derived from the breaking down of 
the rocks of the lithosphere ; a very large proportion comes from extra- 
terrestrial sources. 
Although there is probably no such universal sea of groundwater as 
that pictured by Van Hise, there is yet no reason for not believing that 
surface waters readily penetrate to the deep region, even to the zone of 
rock-fiowage. The lithosphere thus represents merely the flotsam and jet- 
sam of the globe through which the heavier materials may migrate, gen- 
erally inward as individual particles, but occasionally or spasmodically 
outward, in connection with volcanic outbreaks. 
In tfie course of the inward migration of ore materials temporary ore- 
bodies are often localized in the vadose zone chiefly. How much of these 
materials ^are of the recent extra-terrestrial origin and what proportion 
is the product of the rock-decay, is at present , difficult to estimate. The 
meteoritic contribution has yet received, insufficient attention. That it 
may be much more important than has been suspected hitherto is clearly 
shown by recent observations in desert regions. That this is the main 
source of vadose ore-materials now seems not unlikely. It is probable that 
