THEORIES OF ORE DISPOSITION HISTORICALLY CONSIDERED. 333 



deposits. Tliis was in one sense a revival of de Tjeauniont's theories, 

 but the modern standpoint differed in that the existence of a liquid 

 molten interior of the earth had l)een disi)roved l)y terrestrial physic 

 cists. Vogt held that as no connimnication could be established 

 between ore deposits and a heavy interior, they nnist have been 

 deri^•ed from a crust, say. 10. 25, or 50 kilometers in thickness, and in 

 great measure the result of eruptive processes within that crust. 



Emmons (in 1898) acknowledged the importance of the magmatic 

 concentrations of metals in eruptive rock, but thought that in most 

 cases such acctunulations must have been further concentrated in 

 ordei- to produce economically valuable ore deposits. 



During the second decade the influence of Posepny's })aj)er was 

 felt in an increased adherence among outside geologists and mining 

 engineers to the ascension theory. Vogt's views received less atten- 

 tion in this country, because for a long time no ore deposits were 

 studied to which th(^v were found to l)e applicable. The first case 

 Avas that of the titaniferous magnetites of the Adirondacks studied 

 by Kemp, who published his results in 18!>8. 



The year 1000 Avas rendered impoi'tant in the ])rogress of theo- 

 i-etical views on ore deposition by the sinndtaneous appearance of 

 Principles Controlling Deposition of Ores, by Van Hise; Secondary 

 p]nrichment, by P^mmons and Weed, and Metasomatic Processes, by 

 l^indgren, and by the discussions which they prompted. 



Van Hise's article was a l)road, philosoj^hic treatment, based on 

 experimental data, of the whole question of underground circulation 

 as bearing on ore dejwsilion. It Avould be impracticable to give here 

 any complete al)stract of his paper, which is probably familiar to 

 most of you, and onlv a bi-ief statement of such points as bear on the 

 general processes heretofore alluded to will be attempted. His dis- 

 cussion is practically confined to ore bodies deposited from aqueous 

 solutions, which, he considers, embrace the larger ]n'oportion of 

 workable deposits, and he holds that the waters from which these 

 deposits have been made are chiefly of meteoric origin. Their circu- 

 lation is in part descemling, in ])art lateral moving, aiul in part 

 ascending, and during each of these movements they may take up 

 or deposit metallic minerals according as conditions favor either 

 action. This circulation takes place in openings in I'ocks, mostly pro- 

 duced by fracture, and hence is confined to the outer i)ortion of the 

 crust, which he has defined as a zone of fracture as distinguished 

 from a deeper zone, that of flowage, where, under accumulated 

 pressure, deformation produces no macroscopic openings. Its gen- 

 eral tendency is to concentrate from the small openings into larger or 

 trunk channels. The deposits from these waters are distinguished 

 as concentrations (1) from ascending waters alone; (-2) from de- 

 scending w^aters alone, and (3) first from ascending and second from 



