The Pel id and Cam Process. 39 



having a clean-up made by others. It will undoubtedly take 

 the place of the box settler wherever there is sufficient capital to 

 erect it. 



When the whole torta has been washed, the patio must be 

 carefully scraped, and also the interstices between the stones, to 

 remove any particles of pulp, amalgam or mercury. All these 

 scrapings, raspadura, are mixed with the last of the pulp, and 

 are thrown into the settler. The time required to work depends 

 on the number of settlers. It is usually not less than two or 

 three days. 



The tails from the lavadero or Unas consist mostly of iron 

 pyrites mixed with the black sulphides and some ore, their 

 proportion being different with the different ores treated. They 

 are called cabezilla or cabezuelci. They contain some amalgam 

 which is recovered. Formerly* they were carried in wooden 

 bateas to a tank rilled with water, called the pila apuradora, 

 On its surface a wooden bowl, batea apuradora, floats, which 

 is from 1 m. to 1.50 m. in diameter. The man who washes 

 with this batea leans on the side of the pila, and taking hold of 

 the bowl with both hands gives it a peculiar motion, taking up 

 a small quantity of water, whi h after going round the batea, is 

 discharged, taking some of the cabezilla with it. The residues 

 are treated on the patio. Generally the tails from the Unas 

 and lacadero are run over riffled launders, where some of 

 the mercury and amalgam is caught, into two tanks connected 

 with each other, which for a torta of twelve to fifteen tons, are 

 five meters long, three wide and one deep. These are called the 

 tanque and contratanque. The object of the first is to catch all 

 the heavy materials, such as the amalgam and the coarse particles 

 of pulp. Most of the material containing silver and gold is 

 caught here. The contratanque catches only the lighter particles, 

 which are much poorer, and are always kept separate, unless 

 found by assay to be of approximately the same value. The tails 

 from the contratanque run to waste. The materials caught in 

 both tanks are concentrated in the chuza, Fig. 1. Some amal- 

 gam, generally not less than 15 kilos., is caught here, the 

 amount varying with the care that has been taken in the washing. 



*Pkillips' Gold and Silver, p. 344. 



