prepared to receive quicklime dissolved in water. In the same way is poured out the semi-liquid paste. This is called a torta, and contains about 45,000 lbs. Upon this liquid mass four and a half cargas of 300 lbs. of salt is spread, and then a coating of blue vitriol (sulphate of copper) is laid over the whole, and the tramping by mules commences. If the mass is found to be too hot for the advantageous working of the process, then lime in sufficient quantities is added to cool it; and if too cool, then iron pyrites (sulphate of iron) is added. The mules are then turned upon the bed, and for a single day it is mixed most thoroughly together by tramping and by turning it over by the shovel. On the second day 750 lbs. of quicksilver are added to the torta, and then the tramping is resumed.
The most important personage, not even excepting the director, is called "the tester;" for the condition of the ores varies so much, that experience alone can determine the mode of proceeding with each separate torta, and upon the tester's judgment depends oftentimes the question whether a mining enterprise, involving millions of dollars, shall prove a profitable or unprofitable adventure. Perhaps he can not read or write, though daily engaged in carrying on, empirically, the most difficult of chemical processes. To him is intrusted the entire control of the most valuable article employed in mining—the quicksilver. He is constantly testing the various tortas spread out upon the patio; to one he determines that lime must be added; to another, an opposite process must be applied by adding iron pyrites. When all is ready, with his own hands he applies the quicksilver, which he carries in a little cloth bag, through the pores of which he expresses the mercury