226 Geological Sociclj/. 



2ndly, If none is to be found in the immediate vicinity of such de- 

 posits, is there no evidence, derived from the geological constitution 

 of the district, which would lead to the belief that an unstratified 

 rock mav extend under the metalliferous district, and at no great 

 distance from the surface of the country ? 



3rdly, Do there exist metalliferous deposits entirely disconnected 

 from unstratified rocks ? 



With respect to the first of these (juestions, the author shows, by 

 copious references to vvorks on England, Scotland, Ireland, Norway, 

 France, Germany, Hungary, the soutliern Alps, Russia, and the north- 

 ern shores of the Black Sea, that the great mining districts of all 

 these countries are immediately connected with unstratified rocks : 

 and in further support of this solution of the first question, he men- 

 tions the metalliferous porphyries of Mexico, and the auriferous gra- 

 nite of the Orinoco ; but he observes that his knowledge of the 

 mining countries of South America is not sufficient to enable him to 

 state their general geological connexions. 



With reference to the second question, — the probable association 

 of metallic veins with unstratified rocks, though the latter are not 

 visible in the immediate neighbourhood of the former; — the authov 

 gives a section of the country between Valorsine and Servoz, and 

 points out the probable extension of the granite of Valorsine under 

 the Aiguelles Rouges and Breven, composed of protogine, chlorite, 

 and talcose schists, to the immediate vicinity of the mines of Servoz, 

 •which are situated in the latter formation. He also refers the reader 

 for further illustration to the metallic deposits of Wanlockhead and 

 the Lead-hills ; to the mines of Huelgoet and Poullavacn in Brittany ; 

 to those of Macagnaga and Allayna at the foot of Mount Rosa, of 

 Cardinia, Corsica, and Elba ; to the metalliferous veins of the Vosges, 

 Brescina in the Alps, and the Altai chain ; — ail of which occur in 

 districts where unstratified rocks are known to exist. 



The author, however, states that besides the evidence thus afforded 

 of the connexion of igneous rocks with metalliferous deposits, it is 

 necessary to have a knowledge of the stratification of the formations 

 in which mines are worked before any legitimate conclusion can be 

 drawn. 



In reply to the third question, — Do there exist metalliferous depo- 

 sits entirely disconnected from unstratified rocks ? — The author enu- 

 merates the mines of the Netherlands ; those of quicksilver at Idria ; 

 the lead mines of Poggau in the valley of the Mur ; Pezay and Ma- 

 coz in the Tarentaise ; and the veins of galena in the mountain- 

 limestone of the south-west of England. 



The author then gives, as a general illustration of his subject, a 

 sketch of the countries between the Alps and the western extremity 

 of England, and shows that igneous rocks and metallic deposits are 

 totally wanting in the whole of the districts extending from the foot 

 of the Alps across the valley of Lac Leman, the Jura chain, the plains 

 of Franche Comte and Burgundy; and in the oolitic, green-sand, 

 chalk and tertiary formations of the north-west of France, and in the 

 tertiary and secondary formations of England as far as Devonshire j 



