24 S. F. EMMOtfS — THEORIES OP ORE DEPOSITION 



at the School of Mines in Pribram, Bohemia. Although Posepny's 

 views were by no means universally accepted by geologists, especially in 

 America, all agreed that his work constituted a most valuable contribu- 

 tion to the science by its clear definitions of the questions involved and 

 their masterly scientific discussion. The great majority of ore deposits 

 Posepny considered to be of later origin than the enclosing rocks, even 

 those that are found in stratified rocks in apparent conformity with the 

 bedding. Further, that they have been deposited by precipitation from 

 waters of the deep circulation below the groundwater level. The ground- 

 water he conceived descends by capillarity through rock interstices over 

 large areas to rise again at a few points through open channels under 

 the influence of heat. It derives its mineral matter from the bary sphere, 

 or deep region, where the rocks are richer in metallic minerals than near 

 the surface, and subsequently deposits them in open spaces as it ascends. 

 These spaces are either spaces of discission (rock fractures) or spaces of 

 solution, the latter sometimes being formed by ascending thermal waters, 

 even where no previous crack exists. 



Fresh as he was from his controversy with Sandberger over the lateral 

 secretion theory, which he had disproved, at least in its application to 

 the Pribram deposits, he was inclined to view with disfavor anything 

 that flavored of lateral secretion; hence, while admitting that the pres- 

 ence of minute quantities of the metals in eruptive rocks leads to the 

 surmise that they had brought the whole series of heavy metals up from 

 the barysphere into the lithosphere or upper crust, he preferred to as- 

 sume, in the cases which the American geologists had explained as 

 derivation from eruptive rocks in the vicinity of the deposits, that the 

 mineral contents had been brought up by thermal waters directly from 

 the barysphere. Likewise, in the limestone deposits, which their studies 

 show to have been formed by metasomatic replacement, he thought that 

 they must have overlooked some evidence of crustification, and still held 

 to the opinion that such extensive deposits must be mainly the filling 

 of open spaces. Although not explicitly stated, it is evident that he 

 regarded the water of his deep circulation as mainly of meteoric origin. 



Of great practical value was the clear idea conveyed to the mind of his 

 readers of the distinction between the oxidized or altered minerals and 

 the original or sulphide minerals of an ore deposit, a distinction previ- 

 ously pointed out, though less emphatically, by Emmons* and others. 



In the same year appeared the first of a series of important articles on 

 the formation of ore deposits by the Norwegian geologist, J. H. L. Vogt, 

 in which, as opposed to Posepny's views, so much more importance is 

 given to igneous agencies that their different standpoints recall the antag- 

 onisms of the old Neptunist and Plutonic schools. The petrographic 

 studies of Vogt and Brogger had disclosed in basic dikes a tendency of 



♦Colorado Scientific Society, vol. ii, pt. ii, 1886, p. 99. 



