24 Eelations of Trap-Rocks with Ores of Copper. 



little doubt as to the fact of their being contemporary. The 

 mining, which is of old date, has found a source of the pro- 

 duction of nickel in these greenstones of great interest, for 

 it is employed on an ore hithei'to very rare, and whose erup- 

 tive origin cannot be doubted. 



The connection of the Dillenburg schalstein with the ores of 

 copper, is a consideration to be added to those on which we 

 have rested their assimilation to the gabbi'o of the North West 

 of Italy ; on the other hand, their still more intimate connec- 

 tion with the repositories of oligistic iron, diffused abundantly 

 throughout Nassau, identifies them in a still more direct 

 manner with the blatterstein of the Harz. 



We have pointed out this law (" Etudes sur les mines'') vvliich 

 regulates the positions of the oligistic iron of the Harz, es- 

 pecially in the valleys of Lerbach and Altenau, namely, that 

 these ores belong to repositories of contact subordinate to the 

 blatterstein and greenstone, and even inserted accidentally 

 into their own mass. This law is expressed in the mine of 

 Stangenwaage, where we see a thick repository of oligistic 

 iron forming a salbande to the schalstein, and other small 

 beds of less importance entering into the very mass of tlie 

 schalstein and gi-eenstone, always parallel to the general 

 plane of stratification. 



The repositories of peroxide of iron are still more numerous 

 in Dillenburg than in the Harz, and always in the same con- 

 ditions as to position. In order to give an idea of their 

 abundance, we may mention the fact that the foundries in 

 the neighbourhood of Herborn may derive their ores from 

 forty repositories either mined or known. This richness in 

 iron-oreextends to the group of greenstone south from Nassau. 

 There are likewise banks of oligistic iron, of all dimensions, 

 subordinate to the schalstein, so that a certain number of 

 them has been mined to levels accessible by drainings not 

 of an expensive character, while others have furnished ores 

 from time immemorial. These ores, which are rich and of 

 good quality, are sold for not more tlian seven francs a ton. 



Recapitulating wliat has been stated respecting the rela- 

 tions of greenstone and schalstein with metalliferous reposi- 

 tories, we find, then, the trap-rocks, \st, Exerting eni'iching 



