certain Metalliferous Repositories in Depth. 237 



from the native metals of the surface^ which are in crystal- 

 line dendrites and capillary filaments. 



A second zone is characterised by the crystalline and 

 geodic state of the same minerals, by the mixture and va- 

 riety of species, and variety of veinstones {gangues). This 

 zone comprehends almost all the veins. The repository of 

 Rio, in the Island of Elba, so eminently crystalline, likewise 

 belongs to this second zone. The crystallised pyrites, fal- 

 herz, galena, blende, red silver, &c., of the Hartz, Saxony, the 

 Rhine, &c., belong to this category of formations produced 

 by sublimation. The state of the minerals, in fact, reminds 

 us of that of matters brought into existing craters by steam ; 

 and this zone presents us with the emanations of the subter- 

 ranean masses of the preceding zone. 



Lastly, on approaching the surface, we find the phosphates, 

 muriates, arseniates, the native crystalline or capillary 

 metals, and the earthy oxides of the Chapeaux de Fer ; mine- 

 rals which constitute a third zone, as distinctly characterised 

 as the preceding. 



We have not such data as enable us to determine the com- 

 parative thickness of these difi^erent zones. The inferior 

 zone appears to us to have, in some measure, an indefinite 

 thickness, which cannot be measured ; the intermediate zone 

 has never been traversed, and works of 800 yards in depth, 

 carried on in certain veins, have brought to light no varia- 

 tion which indicated the proximity of the mineral substances 

 of the inferior zones. With regard to the superior zone, 50 

 yards would be nearly a medium, and 100 yards a maximum. 

 Its thickness, therefore, is very slight compared with that 

 of the two others ; and it is not of great importance to us, 

 further than that it is the first which presents itself to our 

 investigations. 



This slight degree of thickness in the zone of superficial 

 minerals, ought necessarily to draw attention to the fact of 

 its general preservation, which is such that we can recognise, 

 on the present surfaces, the existence of basins in which the 

 metalliferous repositories, whose formation is anterior to the 

 chalk, have mingled their products with those of sedimentary 



