TEE GENESIS OF OEES 539 



solutions came can often be detected; and peculiarities of shape and 

 position observed which can be explained with difficulty on any other 

 theory. 



Practised miners often point to the richness of ore shoots near the 

 junction or crossing of veins. Indeed such pockets and shoots are 

 usually sought and frequently found where two veins come together. 

 This fact alone may not signify the instrumentality of downward 

 moving waters. But when in connection with it we discover that 

 rich ore shoots are also frequently found at the intersection of veins 

 by faults, and zones of movement so recent or of such shallow depth or 

 limited extent that the faults themselves are not veins, and have not 

 been mineralized except near the intersected veins, and when the ore 

 shoots thus formed occur on that side of the fault plane where they 

 could have been formed most naturally by descending waters, and are 

 wanting entirely in the corresponding place on the other side, then, 

 indeed, we recognize beyond a doubt the agency of meteoric waters 

 in both situations. 



It is often possible where sulphide ores have been deposited in 

 soluble rocks to distinguish between the products of ascension and 

 descension, and here too the latter are frequently of much the highest 

 grade. 



This theory of secondary enrichment which is so frequently re- 

 ferred to in recent mining literature; and is still so little understood, 

 depends, of course, on the existence of a body of primary ore, probably 

 formed by ascending solutions. If there are no ores to be oxidized 

 the downward moving waters will have no metalliferous burden to 

 deposit. But wherever the rocks contain disseminated ore, no matter 

 how small the percentage, there is a possibility of the formation of 

 richer ores through the action of surface waters. And where the 

 primary mineralization was itself comparatively rich, even though 

 not a minable product, there the downward-moving waters may the 

 more readily bring about concentrations of high-grade bonanza ore. 



Bearing in mind this conception of the meaning of " secondary 

 enrichment," and admitting that it is frequently accomplished through 

 the agency of descending meteoric waters, let us briefly consider the 

 conditions under which they are most active and efficient : 



It is a proposition requiring no argument that if by the aid of 

 mineral bearing solutions the ores occurring in veins are to be en- 

 riched, these solutions must enter the veins. And if all the meteoric 

 waters which fall upon the outcrop of a vein or upon rocks contain- 

 ing disseminated ore run off rapidly down the mountainside without 

 remaining to oxidize, dissolve and penetrate the vein with their load 

 of mineral, there can not be any enrichment caused thereby. Further- 

 more, if the work of the surface waters is chiefly destructive mechan- 



