MINERAL VEINS 249 



best idea of the amounts of water in an original deep-seated magma. 

 The percentages are sufficiently high to convince us that the amount may 

 be very great. 



Conclusion 



As a graduate student in the formative period, I was under the instruc- 

 tion and influence of one of the veterans and old-time heroes of American 

 geological science, John Strong Newberry. All the predilections and all 

 the teachings of my honored mentor were against the influence of igneous 

 agents and, like those of a true modern Wernerian, were directed toward 

 sedimentary processes and the waters which we have become accustomed 

 to call meteoric in later years. Every predilection toward these views 

 which could naturally be brought to bear militated against my own con- 

 fidence in igneous forces in nature; but personal contact with the phe- 

 nomena of the metamorphic rocks and the ancient crystallines, with dikes 

 and intrusive masses, with veins and other ore deposits, inevitably pre- 

 sented problems whose solution it seemed impossible to find in any other 

 way than in those outlined in this address. The same course of develop- 

 ment has marked the growth and maturity of many geologists in the 

 period covered by the life of our Society. 



The Society was founded as the microscopic study of rocks became 

 widespread and well established. This statement is tantamount to saying 

 that its beginnings were coincident with intimate and accurate knowledge 

 of the phenomena about which our predecessors more vaguely and gen- 

 erally reasoned. Our later years have been marked by such extended, 

 detailed, and accurate miner alogical, chemical, and structural knowledge 

 of rocks and their attendant phenomena as our forebears never possessed. 

 We have learned our facts and evidence with painstaking care, and we 

 are now interpreting them with confidence and with the conviction that 

 we are at last on the way to the true solution of many hitherto puzzling 

 phenomena. The intrusive rocks and their emissions constitute one of 

 the outstanding groups of causes which, when applied to the ancient 

 strata, to their recrystallization, their soaking with magmatic juice, their 

 digestion and assimilation; when applied to the contact zones; when ap- 

 plied to the long series of veins from the pegmatites, which we also call 

 dikes; to the quartz veins, which we have sometimes thought relatively 

 cold-solution precipitates, and, lastly, which, when applied to the zonal 

 distribution of our metals outwardly from an intrusive mass; in all these 

 cases give us something intelligible, consistent, and illuminating. 



For the future we may only hope that more light may be thrown on the 

 puzzling problem of what great cause or causes periodically start the 



