38 The Patio and Cazo Process. 



labor is less severe. These box settlers can only be workel dur- 

 ing the day, and must, on account of the danger that some one 

 else may remove a part of the amiigam, be cleaned up every 

 night. They cost but little to build, but require the labor of six 

 men, treading, charging and bringing the pulp. As cipitalis 

 scarce, but labor very abundant, the use of this settler is almost 

 universal in Mexico. 



Sometimes the washing of the torta is done in wooden tub set- 

 tlers, Unas, which are usually driven by water power. They are 

 from two to five meters in diameter, and one and a half 

 to three meters deep. The shaft carries four arms, which 

 are fitted with pieces of wood 0.06 m. square and 0.10 m. 

 apart, which reach to within 0.30 m., or less, of the bottom of 

 the tub. In the sides of the tub there are two holes, one 0.8 m. 

 from the bottom, which is 0.15 m. in diameter, from which the 

 tub is emptied ; the other, 0.25 m. from the bottom, is 0.02 m. 

 in diameter, and from it the water overflows, and the tail assays 

 are taken. The axis is geared by wooden gearing to a water- 

 wheel. These tubs were formerly constructed of stone. Three 

 of them communicating with each other, were placed together, 

 and were connected by one large wheel driven by two mules 

 trained especially for the purpose. The first of these tanks, into 

 which the pulp was put, was called Una cargadora, the third, 

 from which the discharge was made, was called discargadora, or 

 discharge tank. In some of the works these tanks are discon- 

 nected, though driven by the same power, each tank being used 

 by itself. '1 he tank is filled one-third full of water, and the axis 

 is set in motion quite rapidly; when mules were used they were 

 set at a full gallop, and a charge of 300 kilos, thrown in. 

 Water is added until it reaches nearly to the top of the tub, and 

 the speed reduced until it is just sufficient to keep the pulp off 

 the bottom. In about an hour the assays taken from the top 

 hole show that the mercury has all settled. The bottom plug is 

 then removed, and the contents of the tub discharged into the 

 settling tanks. This is a much better and quicker method of 

 working. There is no danger of the tub becoming clogged at 

 the bottom, and there is no necessity for constantly cleaning up 

 at very short intervals. The tub can be kept going night and 

 day until the whole torta is washed, without auy danger of 



