THEORTES OF ORE DISPOSITION TII.STORIC4LLY CONRID-^RED. 313 



from oduM" vitrifiiiblc materials. But as there are iionvitrifiable as 

 well as vitrifiahlc materials in veins, so there are secondary veins 

 which liave been filled with iionvitrifiable minerals by the action of 

 water. The ))riiiiary veins he considers to be characteristic of liiLdi 

 mountains, while the secondary veins occur rather at the foot of the 

 mountains, and probably derived some of their material from the 

 primary veins. 



In the second class the foremost place, both in time and in the 

 importance of his actual observations, must be accorded to Dr. 

 George liauer, better knowai by his Latinized name of Agi-icola, a 

 German physician wdio flourished during the first half of the six- 

 teenth century. He spent a great part of his life among the mines 

 of Saxony (Joachimsthal), of wdiich he made a careful study. He 

 wrote in most excellent Latin several works on mineralogy and on the 

 art of mining, which were for centuries standard books of reference 

 on these subjects, and even to the present day contain much of inter- 

 est to the mining engineer. Agricola w-as first and foremost a miner- 

 alogist, and all his work was characterized by acuteness of observa- 

 tion and accuracy of description, though in strong contrast to most 

 of the early writers he did not indulge much in earth-formation theo- 

 ries. He divided mineral veins into " commissuras " (joints or rents), 

 " fibno " (small branching veins), " vense " (large veins or channels), 

 and " terra> canales " (vein systems), and gives a clear account of 

 their size, position, intersections, etc. In theoretical matters he was 

 less definite and satisfactory. 



During all this period the two main subjects of speculation with 

 regard to mineral veins, wdiich term practically included all ore 

 deposits, were (1) their age relative to the rocks in which they were 

 found, and (2) the cause and manner of their filling; and in consider- 

 ing the views put forward on these subjects we must bear in mind 

 that chemistry as a. science only came into existence toward the end 

 of the eighteenth century, hence the ideas which Avere entertained as 

 to the processes that may have gone on within the earth's crust to 

 form metallic deposits were necessarily somewhat vague and fanciful. 



.Vjuong the ideas current in his time Agricola, as a result of his 

 observations, promptly rejected the views that veins w^ere formed 

 contemporaneously with the primary rocks of the globe and that the 

 planets had an influence in the formation of the metals, but he 

 seems to have had very few positive ideas of his own as to their ori- 

 gin, though inclining to ascribe vein filling to material brought in 

 by circulating waters. He still entertained the idea of a lapidifying 

 juice, which he conceived as giving to water the power of absori> 

 ing earth and of cf)rrodiiig metals, and which might have formed 

 fossil casts as well as minerals. His use of the term " fossilia " for 

 both minerals and petrifications, which was retained by subsequent 



