Belations of Trap-Bocks with Ores of Copper. 23 



referring the allure of the metalliferous zones to the direction 

 and inclination of the veins, we find that the zones of enrichment 

 follow inclined lines, diagonal between the inclination and direc- 

 tion of the veins. 



This diagonal allure of the metalliferous zones in veins, 

 is not an exceptional fact ; examples of it are mentioned in 

 the veins which occur on the right bank of the Rhine, from 

 Holzappel to St Goar; but here this fact is explained by the 

 influence and direction of the enclosing rocks. This, then, 

 is still another example of the study of the theory of veins 

 and their geognostic relations serving as a guide to miners. 

 We see, in fact, that vertical works, undertaken to intersect 

 at some depth the ascertained profitable parts in the first 

 levels, might lead to steril zones ; we might be misled by 

 want of success in this way, and be induced to declare that 

 the veins presented no guarantee of richness in depth. 



The subterranean origin of ores in the metalliferous repo- 

 sitories is no longer, in the present day, considered doubtful ; 

 but among the facts which demonstrate this origin, a first 

 place must be assigned to their almost constant connection 

 with the eruptive rocks. All the proofs furnished by the 

 characters of volcanoes, or by certain igneous masses which 

 contain ores, such as the amphibolites of Tuscany, the traps of 

 Kevvena Point, the greenstones of Siberia, the serpentines of 

 Reichenstein in Silesia, &c., may in strictness be rejected, as 

 resulting from local and limited facts, an objection which 

 cannot be made to facts so vast and general as geognostic 

 relations. These relations change their form, they are more 

 or less direct, but when we see them reproduced at the most 

 remote points of the globe, and over vast surfaces — when we 

 find them inscribed on the plans of mines, and in the lan- 

 guage of workmen, we cannot fail to consider them as fur- 

 nishing a most convincing argument in favour of the subter- 

 I'anean origin of ores. 



The greenstones of the neighbourhood of Dillenburg aff"ord 

 a remai'kable case of the dissemination of ores in the very paste 

 of the eruptive rock. It is a dyke, from 5 to 10 yards broad, 

 penetrated with sulpliuret of nickel in crystals or needles, 

 which pcneti'ate the whole paste in such a way as to leave 



