e celebrated Huanchaca and Guadalupe mines in Potosi, Bolivia. In this
description of the process the writer will endeavor to enter into every
possible detail having a practical bearing on the final results; and with
this view he commences with the actual separation of the ores at the
mines.

_Ore Dressing, etc._--This consists simply in the separation of the ore by
hand at the mines into different qualities, by women and boys with small
hammers, the process being that known as "cobbing" in Cornwall. The object
of this separation is twofold: first to separate the rich parts from the
poor as they come together in the same lump of ore, otherwise rich pieces
might go undetected; and, secondly, to reduce the whole body of ore coming
from the mine to such convenient size as permits of its being fed directly
into the stamps battery. The reason for this separation not being effected
by those mechanical appliances so common in most ore dressing
establishments, such as stone breakers or crushing rolls, is simply
because the ores are so rich in silver, and frequently of such a brittle
nature, that any undue pulverization would certainly result in a great
loss of silver, as a large amount would be carried away in the form of
fine dust. So much attention is indeed required in this department that it
is found requisite to institute strict superintendence in the sorting or
cobbing sheds, in order to prevent as far as practicable any improper
diminution of the ores. According to the above method, the ores coming
from the mine are classified into the four following divisions:

1. Very rich ore, averaging about six per cent. of silver, or containing
say 2,000 ounces of silver to the ton (of 2,000 lb.).

2. Rich ore, averaging about one per cent. of silver, or say from 300 to
400 ounces of silver to the ton.

3. Ordinary ore, averaging about 1/2 per cent. of silver, or say from 150
oz. to 200 oz. of silver to the ton.

4. Gangue, or waste rock, thrown on the dump heaps.

The first of these qualities--the very rich ore--is so valuable as to
render advantageous its direct export in the raw state to the coast for
shipment to Europe. The cost of fuel in Bolivia forms so considerable a
charge in smelting operations, that the cost of freight to Europe on very
rich silver ores works out at a relatively insignificant figure, when
compared with the cost of smelting operations in that country. This rich
ore is consequently selected very caref