18 S. F. EMMONS — THEORIES OF ORE DEPOSITION 



many, which was more particularly a country of mines and mining 

 engineers, though among students of this subject there was less solidar- 

 ity of opinion than with the French, and their investigations for a long 

 time were rather on chemical than on physical lines. 



A great impulse to increased accuracy in geological investigation was 

 given by the classic work of G. Bischof, " Physical and chemical geology " 

 (1846-1847), which discusses in a masterly way the processes involved in 

 most of the known geological phenomena, largely on the basis of the 

 author's own researches and experiments, and which may be said to have 

 raised chemical geology to the rank of a distinct science. In the course 

 of his investigations, Bischof, having found that the constituents of the 

 gangue minerals of veins are found in the country rocks, thought it 

 probable that the metals of the sulphide ores might also exist in these 

 rocks in the form of silicates. Later, and independently, Forchhammer, 

 the Danish chemist, in the course of his long continued investigations 

 of the waters of the ocean, detected minute amounts of many of the 

 metals of ore deposits both in sea water and in different varieties of 

 rocks. It was long before the suggestions offered by these discoveries 

 had an}- practical effect on ore deposit investigations. 



The leading authorities (on ore deposits) of that period were Von 

 Beust, Breithaupt, H. Miiller, and Von Cotta. The latter for over thirty 

 years occupied 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 was the standard authority both in Europe 

 and America (through Prime's translation, 1869), maybe 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 minerals, showing, however, a leaning toward the in- 

 filtration or hydrothermal 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 C0 2 or H 2 S are found in the 

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

 on classes of deposits or individual types, do not betray the firm con- 

 viction 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 reference to genesis, 

 would indicate that his genetic ideas were still in a tentative state. 



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

 inadequately explained many of the phenomena of vein deposits, fol- 

 lowed out the suggestions of Bischoff by making an extended series of 

 analyses of the country rocks of veins. Separating previous to anatysis 

 the constituent minerals of the rocks by means of solutions of varying 



