certain Metalliferous Repositories in Depth. - 233 



fissured quartz. Thus, then, to the difficulty of explaining the 

 nature of the transformations of the mineral substance by 

 spontaneous alterations, is joined the impossibility of ascrib- 

 ing to the same origin the partly calcedonous state of the 

 quartz, and the creation of drusy cavities in a substance ab- 

 solutely compact. 



The intervention of water in the phenomena attending the 

 filling up of the superior portion of the vein, is indicated at 

 once by the calcedonous and stalactiform nature of the vein- 

 stone (^angue), and by the hydrated composition of the phos- 

 phates. Let us, then, suppose this intervention favoured by 

 the proximity of the surface, and, on the contrary, suppressed 

 at some depth by the effect of temperature and pressure, and 

 we shall have made an important step towards a probable 

 theory. The veins, in point of fact, have been assimilated to 

 metalliferous solfateros, by which the interior of the globe 

 held communication with the surface, and we may thence 

 conceive how the intervention of water and some other prin- 

 ciple could modify the subterranean emanation which deter- 

 mined the filling up. 



After having studied these modifications of plumbiferous and 

 cupriferous veins, we should still hesitate to generalise our 

 conclusions, if the calamine repositories of Belgium and 

 Rhenish Prussia did not afford us convincing facts, developed 

 on the vastest scale, expressing with more precision the dif- 

 ferences which may exist between the phenomena of the fill- 

 ing up of veins towards the surface, or in deep parts. 



The repositories of calamine, situated in highly inclined 

 beds, with anthraxiferous limestones and psammites, or coal- 

 slates, assume very irregular forms. They may be con- 

 sidered as masses en chapelets, united to each other by 

 sinuous canals, and very much reduced in section when com- 

 pared with that of the widely-expanded portions ; the hori- 

 zontal section of the masses sometimes exceeds 50,000 square 

 yards, as at Moresnet and Dos sur la Meuse, while in 

 the canals it often appears reduced below 100 yards. These 

 irregular chimneys, in communication with the subterranean 

 emanations, appear, in certain cases, to have debouched at 

 the surface into a kind of valleys or basins filled with water, 



