ared
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 as he walks over and over the _torta_, much after
the manner that seed is sown with us. The tester determines when the
silver has all been collected and amalgamated with the mercury. Whether
the tramping process and the turning by shovels shall continue for six
weeks or for only three, is decided by him. When he decides that it is
prepared for washing, the mass is transported to an immense washing
machine, which is propelled by water, where the base substances are all
washed from the amalgam, and then the amalgam is resolved into its
original elements of silver and quicksilver by fire, as already
explained, with the loss of about seventy-five to one hundred pounds of
mercury