206 THE PROBLEM OF THE METALLIFEROUS VEINS. 



a well established reservoir for this solvent in a highly heated condi- 

 tion and at the necessary depths within the earth. Both from its 

 parent mass and from the overlying rocks traversed by it, it may 

 take the metals and gangne. 



In the upward and especiall}^ in the closing journey, meteoric 

 waters may mingle with the magmatic, and as temperatures and 

 pressures fall, the precipitation of dissolved burdens takes place and 

 our ore bodies are believed to result. Gradually the source of water 

 and its store of energy become exhausted; circulations die out and 

 the period of vein formation, comparatively brief, geologically 

 speaking, closes. Secondary enrichment through the agency of the 

 meteoric waters alone remains to influence the character of the deposit 

 of ore. In brief, and so far as the process of formation of our veins 

 in the western mining districts is concerned this is the concei^tion 

 which has been gaining adherents year by year and which, on the 

 whole, most fully accords with our observed geologic relations. It 

 accords with them, I may add, in several other important particulars 

 upon Avhich I have not time to dwell. 



In closing I may state that speculative and uncertain as our solu- 

 tion of the problem of the metalliferous veins may seem, it yet is 

 involved in a most important way with the practical opening of the 

 veins and with our anticipations for the future production of the 

 metals. Every intelligent manager, superintendent, or engineer must 

 plan the development work of his mine with some conception of 

 the way in which his ore body originated, and even if he alternates 

 or lets his mind play lightly from waters meteoric to waters mag- 

 matic, over this problem he must ponder. On its scientific side and 

 to an active and reflective mind it is no drawback that the problem 

 is yet in some respects elusive and that its solution is not yet a matter 

 of mathematical demonstration. In science the solved problems lose 

 their interest ; it is the undecided ones that attract and call for all 

 the resources which the investigator can bring to bear upon them. 

 Among those problems which are of great practical importance, 

 which enter in a far-reaching way into our national life and which 

 irresistibly rivet the attention of the observer, there is none with 

 which the problem of the metalliferous veins suffers by comparison. 



