Continuity of Metalliferous liepositories in Depth. 357 



pletely abandoned, when, in 1840, MM. Rhodius, assisted by 

 the advice of tlie skilful M. de Dechen, resumed tlie works, 

 conducting them by the aid of a steam-engine. The minerals 

 have again been reached, and this mine has recovered, in 

 productiveness, the rank which it never would have lost, if 

 the first miners had placed more confidence in theoretical 

 principles. 



In a class of veins less regular in character, namely, veins 

 of contact, we find some fine examples of richness continued, 

 and even further developed, as we increase in depth. 



At Almaden, the cinnabriferous veins are explored to 300 

 metres ; the richness is always perfectly kept up, and the 

 Spanish engineers have entire confidence in the works even at 

 the bottom. 



The beautiful vein of Monte-Catini, in Tuscany, was 

 wrought for nine years by the honourable M. Porte, whose 

 life was so laboriously spent in re-opening the mhies of that 

 country. The produce had always been moderate ; and M. 

 Porte' s confidence was shaken, when the companv that 

 succeeded him found, at 80 metres, and below the first 

 level, one of the finest accumulations of variegated and 

 pyriteous copper that can be mentioned in the history of 

 mines. For ten years the works have been carried down- 

 wai'ds, without any impoverishment, and tlie miners have 

 confidently undertaken very extensive works (among others 

 a level of 1400 metres), directed by tlie engineer Schneider, 

 which must secure a considerable increase of depth. 



Such examples shew the generality of the principle of the 

 continuity of minerals in depth ; we shall further mention a 

 few others to prove that, in a great number of localities, the 

 distribution of minerals has been much more constant ac- 

 cording to the inclination than according to the direction. 

 Thus, many veins present in direction some rich zones, sepa- 

 rated by poor or barren zones usually much more important ; 

 by following the veins, according to their inclination, it has 

 been found tliat these zones were continuous, that they re- 

 peated themselves with tlie same characters in the lower 

 stages, even to considerable depths, so that the metalliferous 

 parts formed a kind of columns or chimneys ascending from 



