Sketch of the Mine of Pasco. 55 



Upon the gres, rests the white Alpine limestone, (so called from 

 feeing the same in form with that of the Alps,) as in the acclivity of 

 Uliachin, Yanamente, chain and pampas of St. Juan, shores of 

 Quinlacocha, Colquyurca, T^inchos and Pargas. The conglomerate is 

 well distinguished, as in the rocks of Suco, and Chaquilguanca, where 

 it makes a grand fortification, of more than three hundred yards high. 

 The calcareous formation is the most extensive, since it may be said 

 to be the most common matrix of metals of silver in this place ; all 

 to the east of Yauricocha, the contiguous rough grounds and hills of 

 the plain of Bourbon, are composed of this rock, which forms hori- 

 zontal strata, inclining to the east, and in some parts, as in the bro- 

 ken land of Quinlacocha, and shores of the River Ranca, it is fre- 

 quently observed in the zigzag form ; and in the broken land of 

 Uliachin and St. Juan, the strata appear perpendicular, from the ex- 

 cavation which the taza of Yauricocha forms. This Hmestone is blue, 

 and semi-compact, and contains veins of calcareous white spar ; the 

 shells are scarce, and in it are some metallic strata, principally lead, 

 and sulphureous pyrites, which produce silver. In the hill of Vin- 

 chos, this formation is more extensive, and Hes more distinct, as is 

 seen in the road from Pasco to this point, and principally in the height 

 of Chaguanaco, and rocks contiguous to Chaquilguanca ; but de- 

 scending to the deep uneven ground of Janio, the gres insensibly dis- 

 appears, and passes to an argillaceous esquito. Vinchos is rather 

 valuable, owing to its strata being composed of lead and pyritous 

 minerals ; it has tliree peaks which are called Maman Vinchos, Gua- 

 quan Vinchos, and Riuam Vinchos. All three are composed of 

 blue hmestone, half decomposed on the surface ; presenting inequal- 

 ities and roughness, which prevent the traveller from ascending to its 

 summit ; the calcareous strata are almost horizontal, and those of 

 the lead veins have the same direction ; and are in the mine from a 

 half a yard, to a yard wide. In that of Descubudora, which is the 

 most celebrated, the stratum is about twelve inches broad, and one is 

 composed of pyrites, which are ferruginous and very compact; this 

 prevents the mine from being worked to advantage ; ahuost all this 

 ledge is traversed by metallic strata, the minerals of which, yield at 

 least from eight to thirty marks the cajon ; but there is a great in- 

 convenience arising from the want of instruments and combustibles, 

 for the foundery. On the north, tlie soil continues forming slopes, 

 and contains many strata of paces in the gres, extending almost as 

 ■far as the village of Mosca, in the neighborhood of which, are found 



