326 THEORIES OF ORE DISPOSITION HISTORICALLY CONSIDERED. 



thirty years occn])ied the chair of geology at Freiberg, during 

 which time he had opportunities of visiting most of the important 

 mines of Europe. His text-book on ore deposits (1853-1859), which 

 up to the end of the third quarter of the century w^as the standard 

 authority both in Europe and America (through Prime's transh^- 

 tion, 1869), may be assumed to be a good exponent of the knowledge 

 of the time. It gives a fair-minded statement of all the theories 

 which had been given to account for the formation of vein min- 

 erals, showing, howcA^er. a leaning toward the infiltration or hy- 

 drothermal theory of vein filling, based on the fact that some of the 

 most common constituents are found in existing thermal waters, and 

 that thermal waters containing COo or HoS are found in the deeper 

 workings of some mines. In general, however, his views, whether 

 on classes of deposits or individual types, do not betra}' the firm 

 conviction that would result from an exhaustive and systematic 

 study. Moreover, the fact that his classification of deposits is based 

 on the more or less accidental character of form, without any ref- 

 erence to genesis, would indicate that his genetic ideas were still in 

 a tentative state. 



In 1873 Prof. F, Sandberger, feeling that the current theories 

 inadequately explained many of the phenomena of vein deposits, 

 followed out the suggestions of Bischof by making an extended 

 series of analyses of the country rocks of veins. Separating 2:»revi- 

 ous to analysis the constituent minerals of the rocks by means of 

 solutions of varying densities, he succeeded in demonstrating to his 

 own satisfaction that the characteristic minerals of different depos- 

 its are contained in the basic silicates of the adjoining rocks, and in 

 1880 propounded his theory of lateral secretion, according to which 

 the mineral contents of veins are derived, not from some unknown 

 depth, but from the immediate wall rock, being brought in by 

 percolating waters which are not necessarily at a very high tem- 

 perature. As against the thermal-spring theory, he argued that a 

 very small proportion of known thernuds contain any of the metal- 

 lic minerals whatever, and none in the state of sulphides; further, 

 that the deposits observed in their channels have been precipitati'd 

 in immediate proximity to the surface and under physical and chem- 

 ical conditions that differ essentially from those that must have pre- 

 vailed at the depths at which veins were formed. 



Sandberger's theory, though for a time it found many adherents, 

 was bitterly contested, especially by Stelzner, Von Cotta's successor 

 at Freiberg, and by Posepny, professor at the Mining School of Pri- 

 bram, in Bohemia. They maintained that the facts in their respective 

 districts disproved the lateral secretion theory in the restricted sense 

 in which Sandberger employed it, and they demonstrated by a repe- 

 tition of his analyses that, oAving to imperfect methods, he had not 



