Continuity of Metalliferous Bepositories in Depth. 347 



The only prominent facts which may be cited as dis- 

 coveries of the nineteenth century, ai'e, 1^^, The washing of 

 the auriferous sands of the Oural, w^hich have increased to 

 an annual produce of more than 10,000 kilogrammes of 

 gold.* 2d, The copper-mines w^-ought in the island of Cuba, 

 in the neighbourhood of Santiago, which were opened in 1833, 

 on the old works, and now send 40,000 tons of the mineral 

 to Swansea, with the mean title of 16p. 0/0, that is to say, 

 6,400,000 kilogrammes of copper. Zd, The Calamine mines 

 of Belgium and Rhenish Prussia, which, from a produce 

 scarcely w^orth naming, now yield 12,000,000 kilogrammes 

 of zinc. 4/A, The lead-mines of Missom-i and Illinois, the 

 importance of which is not yet appreciated, but which, it is 

 said, would produce 30,000,000 kilogrammes of lead. 5M, 

 The copper-mines of Lake Superior, the working of which is 

 projected on a large scale. t 



These achievements of the nineteenth centiu'y are import- 

 ant ; but they would not have been sufficient to meet the in- 

 creased consumption, if the metallifei'ous districts previously 

 known and wrought, had not been managed in such a manner 

 as likewise to increase their productiveness. The mines of 

 Cornwall have been conducted with such skill that it has 

 continued in the first rank for the production of copper, and 

 divides the monopoly of tin only with Banca and Malacca ; 

 the mines of Derbyshire, Cumberland, and Siei'ra de Gador, 

 continue to be the most important for lead ; those of Ger- 

 many have preserved their superiority for argentiferous leads, 

 and for the treatment of minerals mingled with silver, arsenic, 

 lead, nickel, cobalt, &c. Silesia has ahvays continued first 

 in the fabrication of zinc ; Almaden in that of mercury. The 

 mines of Mexico are always the principal source of the silver 

 employed in commerce. 



It is, therefore, always the same metalliferous district? 

 which constitute the mineral riches of the globe. If we ex- 

 amine the progress followed by the subterranean works in 

 these districts, we perceive that a considerable extension has 



* Kilogram equal to 21b. 3oz. avoirdupois. 



t We may add to the above tiie very productive mines of red copper-ore and 

 green and blue malachite of Hurra-lJurra, in Australia. Kd. 



