n encountered; whilst ores
of 1,100 ounces have been frequently exported to Great Britain.

The almost fabulous wealth obtained from the silver mines has been
shown in the foregoing pages, and these mines are far from being
exhausted at the present day. The importance of the Pachuca mines is
shown by the statement that they produce six million ounces of silver
and 30,000 ounces of gold yearly. Of the population of the city, of
forty thousand souls, seven thousand are employed underground.

All of the Mexican states are silver bearing, although those which
contain the famous mines are the most important, as:--Sonora,
Chihuahua, Sinaloa, Zacatecas, San Luis Potosi, Guanajuato, Queretaro,
Hidalgo (Pachuca), Mexico. All these states contain numerous mining
districts--cities, towns, camps--which it would take too much space
here to enumerate. With the exception of the few modern installations
most of the mines are worked by the primitive Mexican system of winding
up the ore in raw-hide sacks, hauled by means of cables made from
_maguey_ fibre, upon a mule-actuated windlass--the _malacate_. In some
cases the miners carry huge pieces of ore on their backs, from 100 lbs.
to 200 lbs. in weight, along the galleries to the shaft. Interior
transport and haulage are primitive.

The principal ore of silver is the sulphate, although native silver is
also freely encountered in some districts. The ores were very generally
decomposed to a depth of about 300 feet. Argentiferous galena is
plentiful, and silver is freely found in conjunction with copper ores.
The _caliches_, a chalk-like substance, easily worked, is another rich
form of occurrence of the metal, and there are others less important.
Various different methods of separating silver from its ores are used;
the prevailing ones being those of smelting, lixiviation, and the
_patio_ process, which last has accounted for 90 per cent. of the
production. Indeed, the recovery of silver by the _patio_ process has
always been one of the most important industries of Spanish-American
countries, especially in Mexico, Peru, and Chile. In Mexico it has been
employed continuously since the year 1557, when it was invented by
Medina at the _hacienda_ Purisima Grande. This was the first
application of amalgamation to silver ores, and permitted the treatment
of the vast quantities of low-grade ores, which did not pay to smelt.
To-day great quantities of ore are still treated by this method. The
p