TllKORIES OF OKK DISPOSITION 1 1 ISTORKWr.LV OONRTDKRED. 315 



coiisidcriMl (lull (he iiiiitcriiil ol' \('iiis. oriiiiiially (lie siuiic as the 

 inclosing- rock, had hccii allcrcd by some saline solution and thus prc- 

 parcnl for its final transformation into metallic minerals. The ahoxc, 

 which mi<iht be calUnl conversion theories, do not necessarily assume 

 that veins are mechanically formed cr-acks. and hence of more recent 

 formation than the inclosing rocks. 



Von Tre.bra, a director of mines avIio Avas seeking for facts to aid in 

 theii- exploitation, thought the changes observed in moinitains 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 rei)lacing 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. 



Ijehmann, 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 nautre is carrA^ng 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 amcmg 

 practical miners exon at the present day, probably because it appeals 

 almost exclusively to the imagination. 



Delius, Gerhard, and Lasius had the general idea that A'eins were 

 fissures formed later than the inclosing rocks, which had been filled 

 by materials brought in by circulating Avaters. The last Avent so far 

 as to suppose that these waters contained carbonic acid and other 

 solvents AAdiich enabled them to gather up metallic materials in their 

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

 modern vieAvs, but he Avas in doubt Avhether the metals Avere contained 

 in the rocks as such, or whether the soh^ents possessed the power of 

 turning the substances they encountered in one place into lead and in 

 another into sih'er or some other metal. 



Of more permanent value Avere the Avorks of Von Oppel ( 17-10) and 

 de Charpentier (177S), Avho Avere successiA^ely directors of the Saxon 

 mines previous to Werner. 



Von Oppel was the first to distinguish bedded clejiosits (lager- 

 gange), or those Avhich lie ])arallel Avith the stratification, from true 

 veins. He also gaAe to the small branches from a main vein the name 

 of "stringers'' (triimmer), and noted that veins sometimes shift or 

 fault the strata they cross, in Avhich case he calls them '* shifters " 

 (Avechsel). He laid stress on the importance of the causes Avliich have 

 produced rents or fissures in the earth, and shoAvs hoAv in the forma- 

 tion of mountains the rocks, being exposed to great desiccation and 

 violent shocks, might split one from another, thus producing rents 



