NOTES ON BRAZIL. 



465 



* theless none of these cases prove that the process has not been continually 

 going on, and that there is no recently formed gold. Old Miners say, 

 that it grows, that beds formerly wrought contain now a larger 

 quantity than it is possible to suppose their ancestors would have 

 left in them ; to me, however, the evidence of this is by no means 

 satisfactory. 



On the upper surface of this Serro, and even on most of the clays 

 over which we passed, as has been frequently noted, there is a large 

 quantity of Feldspar and Quartz in nodules, yet it is said that no Gold 

 was ever found among them ; indeed these nodules seem to me to have 

 been formed in a very different period, and by a very different process, 

 from that which has produced the auriferous veins. That none but 

 these veins are the natural and native beds of the metal, I think must 

 be evident to all who have examined the mines with care, and I hope 

 will be rendered probable to those who may attend to the descriptions of 

 them, which shall presently be given ; yet these veins are so narrow, so 

 hard, so little affected by the action of water, and so completely secured 

 from attrition of every kind, except on their outer edges, that it is impos- 

 sible to suppose the quantity v^4lich has been obtained from the Mine 

 of St. John's should be derived only from the veins which terminate in 

 it. A portion of precious dust must have existed in the soil of the 

 mountain, and have been brought down from the surface by the waters 

 which have flowed over it. It was placed there, I conceive, by the 

 same means as the mica was, when the solid rocks were decomposed. 



The Caldeiraos, or those parts in the body of the mountains where 

 the metal exists in large masses and almost pure, are of two kinds : those 

 in the solid Granitic Rocks seem to be the chambers, whither the men- 

 struum which held in solution the precious ore, has tended, where it has 

 rested and deposited the metal with which it was saturated : those 

 which are found in the softer mountains appear to be of later formation, 

 were probably the lower parts in the bed of a current, a lake, or the 

 ocean, whither the heavy metal, previously existing in the form of dust, 



among the mud of its bottom, has tended, and been finally collected. 



3 N 



