736 C. R. VAN RISE 



These igneous materials undoubtedly do in many cases bear 

 metals out of which ores are made. But in few instances are 

 they ores as igneous rocks. Igneous rocks so rich in iron as to 

 serve as ores have been found on a very small scale. Vogt x 

 holds that certain sulphide ores are produced directly by pro- 

 cesses of differentiation of igneous rocks; but while I do not 

 deny this, I also would not unqualifiedly assent to it. How- 

 ever this may be, there is fair agreement on the part of all 

 that the great mass of the metals which come from the igneous 

 rocks are derived from them through the agency of underground 

 water, and that the ores which are now worked by man are pre- 

 ponderantly concentrates from the igneous rocks, or from the 

 sedimentary rocks, or from the two combined. But if some 

 ores have directly solidified as magma, thev do not come within 

 the scope of the discussion tonight; for I said at the outset 

 that only ores produced by underground water would be con- 

 sidered. Such ores are probably derived for the most part 

 from the upper 10,000 meters of the crust of the earth. 



My third premise follows directly from the considerations 

 already given : If the waters below the zone of fracture do ?wt 

 circulate vigorously, a?id if vigorous circulation by underground 

 water be necessary i?i order that ore deposits be produced, it 

 follows that the waters which perform this work are of meteoric 

 origin. They are the waters which fall from the clouds upon 

 the earth and sink into it. I do not deny that some small part 

 of water concerned in the production of ores may be derived 

 from below the zone of fracture ; I do not deny that the igneous 

 rocks rising from below bring with them small amounts of 

 water; but these amounts are insignificant — are inappreciable 

 in quantity as compared with the vast amount of water which is 

 necessary to do the work of ore deposition. We know to a cer- 

 tainty that the great mass of underground circulating waters 

 are of meteoric origin. For instance, if a well be drilled at 

 Chicago through the limestones and shales near the surface 



1 J- H. L. Vogt : Zeitschr, fur prakt. Geol., January and April 1893, October 1894, 

 April, September, November, December 1895. 



