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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Nov. 21, 



as Permian, quite detached from the rest of this formation, with 

 which it has been grouped merely from its general resemblance 

 in mineral character. It rises in the midst of the eastern plateau 

 or " Puna " (as it is generally termed by the natives) as a steep 

 ridge, broken in the centre so as to form a steep anticlinal, with the 

 strata dipping respectively to west and eastward. The centre of 

 this anticlinal is formed of red sandstones with gypseous seams ; at 

 Penas the gypsum frequently occurs in crystalline plates of great 

 purity ; above these, to the westward, are some beds of coarse red 

 conglomerate, which, in turn, are succeeded and covered by a second 

 series of red sandstones. At Penas the gypseous sandstones which 

 form the anticlinal have a strike of N". 20° E., and, after dipping at 

 a high angle to the east, gradually become less inclined, and rise, 

 with a reverse or westerly dip, in a little hill to the eastward, thus 

 forming a shallow intermediate basin ; the red conglomerates which 

 should overlie them do not come to the surface. 



The well-known copper-mines of Corocoro (which, besides the 

 supply for the home-consumption, exported from the port of Arica 

 in one of the last years washed copper of the local value of 

 2,450,000 dollars) are situated in the red sandstones of this forma- 

 tion, and have been worked by the Indians from time immemorial. 

 They were found in operation at the time of the Spanish conquest, 

 and since then, up to the present date, have gradually increased in 

 importance, notwithstanding that many of the mining and metal- 

 lurgical processes are conducted in a manner more indicative of the 

 times of the Inca dynasty than of the nineteenth century. 



The copper occurs native as metallic grains or larger masses, dis- 

 seminated irregularly in certain beds of sandstone ; but combinations 

 of copper with oxygen, arsenic, &c. are also found occurring in a 

 similar manner to the west of the line of fault ; the metallic copper, 

 however, is the main object of exploration, and in a state of powder, 

 resulting from the crushing and washing of the cupriferous sand- 

 stones, is exported in large quantities to Europe under the name of 

 " copper-barilla." The want of coal or wood in this barren region 

 prevents the other or mineralized ores of copper being worked or 

 concentrated to a sufficiently high percentage for exportation, — the 

 only smelting works in operation for the supply of the country, and 

 for some little ingot- copper for exportation, being supplied with fuel 

 from the excrements of the Llamas — it being considered that 100 

 quintals (each quintal = 101| lbs. English) of Llama dung will 

 smelt 80 quintals of " copper-barilla*.' The furnaces employed are 



* Owing to a wise provision of nature, the Llamas, when pressed by the calls 

 of nature, do not, like the sheep, scatter their excrements over the ground at 

 random, but resort to fixed spots, which they select themselves for the purpose, 

 which circumstance enables an almost incredible quantity of this material (espe- 

 cially when we consider that in size the excrements do not materially exceed 

 those of the sheep) to be collected for the use of the copper-smelters, and for the 

 general supply of the iidiabitants with fuel in a country otherwise destitute of 

 combustibles. The other animals allied to the Llama' (Alpaca, Vicuna, and 

 Guanaeo) also follow this laudable custom. 



