OF ATACAMA AND COQUIMBO. 263 



When &quot;brought up from the mines, ores are deposited in the canchas, as the enclosed yards 

 are called. All those which will amalgamate with quicksilver are broken in pieces of about 

 half a cubic inch, and assorted in three piles of different qualities, according to their richness. 

 So well versed in ores do the men employed in breaking them become, that they tell by the touch, 

 rather than by weight, to which of the piles a stone properly belongs. The fracture of the 

 richest ores is most asperous. Other ores, denominated metales frios, comprising sulphurets, 

 arseniates, &c., from which the silver cannot be obtained by amalgamation, are left in pieces 

 just large enough to be easily transported, and are sent out of the country for reduction. When 

 broken, and the accumulated dust is expelled by winnowing, as they do chaff from wheat, by 

 tossing it in the air, the share of each proprietor is carefully weighed, and disposed of in con 

 formity with his directions. There is a large quantity of ore, however, of which no use has 

 been made to the present time, because the proportion of silver it contains is too small to justify 

 tte expense of transportation and amalgamation. Where water is so scarce, even for the latter 

 purpose, and mule-hire so extravagant, unless the ore will yield fifteen marks to the cajon ($150 

 for 6,400 pounds), it remains in a heap before the mouth of the mine. Of this character there 

 are now lying at El Bolaco ores that are estimated to contain not less than $&amp;gt; 20,000,000. A rail 

 road connecting with that from Caldera has been pronounced practicable, by following the bank 

 of the stream until it turns the northeast flank of Chanarcillo, and thence down to El Bolaco ; 

 and this silver cannot lie in waste much longer. 



For extraction of metal from the ores, there are eighteen establishments in the district of 

 Copiapo all of them the property of companies or individuals.* Thereis strict accountability in 

 each of them, which offers security to the miner, independently of the criterion which the analysis 

 of his ores affords him. In seventeen mills the system of Cooper is followed; in the other the old 

 mode of treading the amalgam until the silver and mercury are thoroughly incorporated, when 

 the earthy portions are washed away, and only the combined metals are left. Both men and 

 animals are sometimes weeks in treading the metallic tortas (cakes). Most of these establish 

 ments are within the city the others at various points along the stream above it. The 

 machinery and mode of operations are as follows : 



A circular block of granite, about three feet in diameter and fifteen or sixteen inches thick, is 

 secured to an upright revolving shaft. This stone revolves over the flat surface of another 

 block of the same material, placed at the bottom of a strong wooden tub, partially filled with 

 water, and into which the ores are thrown, in the condition in which they come from the mine. In 

 the course of a few hours, according to the character of the ores, they may be ground between 

 these two stones as fine as flour. Thence they are drawn into large vats or tanks, and the 

 heavier portions having settled at the bottom, the clear water is drawn off. In a second apart 

 ment there are other tubs of wood, somewhat larger than those used in the grinding process. 

 These have discs of iron at the bottom, with a single groove from the centre to an aperture on 

 one side. To an axis revolving vertically within each tub there are four iron arms, bent into 

 this form, 



whose motion with the axis or shaft preserves a constant agitation of the semi-fluid mass poured 

 in from the vats. A due portion of quicksilver being added, the two metals will have become 

 united, and sink to the bottom in six or eight hours, leaving the earthy substances still in solu- 



