( 220 ) 



On the Origin of Quartz and Metalliferous Veins. By Pro- 

 fessor GusTAV BISCHOF, of Bonn.* 



[Concluded from vol. xxxix. p. 132.J 



Solutions of various substances came in contact at the 

 points of intersection of two veins of different kinds. It 

 could easily happen that the substances contained in the one 

 liquid might have a precipitating effect on those of the other, 

 and thus give rise to deposits which would not otherwise 

 have been formed. 



V. Oeynhausen and v. Dechenf state, that, in the Carclaze 

 tin mine, at St Austle, small veins of tin cross one another 

 without change of position, and that the richest tin ores are 

 found at the points of intersection. A phenomenon of this 

 kind is, indeed, not difficult of explanation. If, in the older tin 

 veins, vein-masses were deposited in which non-metallic mat- 

 ters predominated, and if those veins were traversed by fissures 

 at a subsequent period, then these non-metallic substances 

 would operate with a precipitating effect at the points of inter- 

 section on the tin ores, which were dissolved in the liquid cir- 

 culating in the newer fissures. A small variation in the 

 nature of this liquid from that which had previously circu- 

 lated in the older fissures — it might be a qualitative or a 

 quantitative one, or only a change of temperature — ^would fa- 

 vour this state of things. No one can doubt that an exchange 

 must have taken place ; for a richer deposition of ore could 

 only have resulted from the disappearance of the barren 

 rock. 



It will hardly be attempted to explain all the pheno- 

 mena which have now been enumerated, such as the influence 

 of the adjacent rock on the nature of the vein-masses, the 

 penetration of the adjacent rock by the ore, the difference of 

 the latter in the veins and in the adjacent rock, the increased 



'** The delay in the publication of the conclusion of Professor Bischof's 

 Memoir has been caused by our never having received the remainder of 

 the translation from the gentleman who undertook it. — EdiU 



t Karsten's Archiv, 1838, vol. xvii., p. 19. 



