THE SPECULATIVE PERIOD 7 



The views of most of these early writers were rather curious than in- 

 structive, yet some of them, especially those of men who had the largest 

 practical experience in mines, are remarkably suggestive. 



Rosier, the earliest recorded mine superintendent, recognized that 

 veins differ from ordinary cracks in the rocks only by being filled with 

 metallic minerals, but did not speculate on their genesis. Becker and 

 his commentator, Stahl, both professors of medicine, assumed in a gen- 

 eral way that mineral veins were original cracks in the rocks contain- 

 ing matter that had been changed into vein minerals by some exhala- 

 tions from the interior. Henkel supposed further that certain kinds of 

 rock or stone which served as matrices were favorable and even abso- 

 lutely necessary to the formation of vein minerals. Zimmermann, who, 

 like Henkel, was a chemist rather than a miner, considered that the 

 material of veins, originally the same as the enclosing rock, had been 

 altered by some saline solution and thus prepared for its final trans- 

 formation into metallic minerals. The above, which might be called 

 conversion theories, do not necessarily assume that veins are mechanic- 

 ally formed cracks, and hence of more recent formation than the enclos- 

 ing rocks. 



Von Trebra, a director of mines who was seeking for facts to aid in 

 their exploitation, thought the changes observed in mountains took place 

 slowly under the influence of heat and humidity, and expressed his 

 idea of conversion as applied to veins more distinctly as the taking away 

 of one constituent of a rock and replacing it by another. The agent of 

 the transformation he called putrefaction or fermentation, by which 

 names he wished to designate some unknown force which produced the 

 chemical changes observed in the rocks. 



Lehmann, a mineralogist and also a director of mines, supposed that 

 the veins found in mines are only the branches and twigs of an immense 

 trunk that extends to a great depth in the bowels of the earth, where 

 nature is carrying on the manufacture of the metals, and whence they 

 travel toward the surface through rents in the rocks in the form of 

 vapors and exhalations, as the sap rises and circulates through plants 

 and trees. This general view is popular among practical miners, even 

 at the present day, probably because it appeals almost exclusively to the 

 imagination. 



Delius, Gerhard, and Lasius had the general idea that veins were fis- 

 sures formed later than the enclosing rocks, which had been filled by 

 materials brought, in by circulating waters. The last went so far as to 

 suppose that these waters contained carbonic acid and other solvents 

 which enabled them to gather up metallic materials in their passage 

 through the rocks. In this respect he approached closely to modern 



