Continuiti/ of Metalliferous Hepositories in Depth. 351 



be found immediately subordinate to the eruptive rocks, or con- 

 tained in the sedimentary beds, they follow a rule of contact 

 very different from the eruptive masses, and follow each other 

 irregularly in certain seams of stratification and cleavage. 



In these two classes of repositories, theory points out to 

 us the metalliferous substances as posterior to the inclosing 

 formations, except in those cases where they are integral 

 parts of the eruptive rocks, or vphere they have been strati- 

 fied along with the sedimentary deposits, by the effect of 

 a contemporaneous metamorphism. Moi'cover, a great num- 

 ber of observations authorise us to conclude, that the me- 

 talliferous substances originate in subterranean phenomena, 

 the seat of which must be below the solid crust of the 

 globe. 



Such are the general principles which geology applies to 

 mines, and which may be considered as demonstrated. In 

 every metalliferous district, these principles are influenced 

 by local considerations which often determine the particular 

 rules, but these rules always remain subordinate to the gene- 

 ral principles. 



This theory of metalliferous repositories, the constant and 

 often bold applications of which secure a kind of classical 

 superiority to the mines of Cornwall and Germany, may like- 

 wise become the occasion of very unfortunate results, by be- 

 ing improperly understood. The first condition, for example, 

 is to establish clearly the distinction between regular and ir- 

 regular repositories. The individual who, disregarding all 

 the works of his predecessors, would expect to find the rules 

 that apply to veins applicable to irregular repositories, such 

 as those of Sierra de Gador, would necessarily be led to dis- 

 pute these rules ; to maintain that in mines, every thing is the 

 effect of chance ; in a word, to envelope the whole doctrine of 

 geology in the consequences of his own error. Let us sup- 

 pose, on the contrary, that these same repositories of Sierra 

 de Gador were examined by an experienced miner, such as 

 MM. Paillette or Gomez de Salazar, they would be charac- 

 terised at once as irregular ; then the interpretation of the 

 circumstances of their irregularity and disposition would 

 shew that they succeed each other according to certain 



