1848.] Metalliferous deposits in the Sub- Himalayas. 141 



stone, and conglomerate throughout Mexico ; where also graywacke 

 is very rich in metals ; the metalliferous rocks also abound in horn- 

 blende ; and the porphyries are very rich in gold and silver. There is 

 scarcely any variety of rock that has not been found to contain metals ; 

 and in South America especially, the richness of the veins, is for the 

 most part totally independent of the nature of the beds they intersect. 



In Potosi, the richest mines are at a vast elevation, the strata chiefly 

 composed of a yellow, firm, argillaceous slate, with veins of ferruginous 

 quartz, which constitute the matrix of the silver. 



Reasoning from the above facts, it would appear that we must only 

 expect to find veins of the precious metallic ores, at elevations very 

 superior to Darjeeling, and that we must first discover and explore those 

 regions, where transition rocks overlay the gneiss, granite, and syenite. 



Doubtless the gneiss, at elevations equal to Darjeeling, and even less, 

 also contains metallic veins, especially as the rock, from the abundance 

 of hornblende, coincides in character with the Cordillera gneiss ; but 

 all the streams being destitute of gold deposits, prove that there are no 

 superficial veins of that metal. By proper search lead, combined with 

 silver, would very probably be found. 



The total absence of Volcanoes does not militate against the hope of 

 discovering metalliferous veins, as the Ural mountains, rich in metals, 

 are as destitute of volcanoes, as the Himalayas. 



The sub-stratum of the whole of the mountains around Darjeeling, 

 must be considered of a primitive and metalliferous character, being 

 chiefly hypogenic gneiss rock. I am convinced that abundant veins 

 of copper, lead, and iron ores, will be found at low elevations ; and 

 that native gold, and sulphuret of silver, will be found in the higher 

 regions, as throughout the elevated land of Thibet, gold is an abun- 

 dant production, in the debris of rocks of similar stratification, forming 

 the alluvia of the rivers, while cethiops-mineral or proto-sulphuret of 

 mercury, is also there abundantly found. 



The snowy range forms the barrier to each region, and the forma- 

 tion being integrally the same, it is far from probable that ores are 

 only confined to the north-eastern aspect, — the probability being in 

 fact, that the facility with which abundance of the precious ores are 

 found in Thibet, solely arises from the face of the country, which is 

 almost destitute of wood. 



