In the beginning of the 18th century, the quantity of gold and silver coined at Mexico, (which generally coincides with the quantity produced by the mines) was only from five to six millions annually ; but the amount has been constantly on the increase for the space of 113 years, excepting the period from 1760 to 1767, so as to have been tripled in 50, and sextupled in 100 years. This enormous increase observable in late years, is attributed by M. Humboldt to a number of concurring causes, particularly to " the increase of population on the table land of Mexico, the progress of knowledge and national industry, the freedom of trade conceded to America in 1778, the facility of procuring at a cheaper rate the iron and steel necessary for the mines, the fall in the price of mercury, the discovery of the mines of Catorce and Valentiana, and the establishment of the Tribunal de Mineria." This progress of the mining operations is exhibited by the following Table of the gold and silver given into the mint of Mexico in periods of ten years.
The other metals in New Spain have been greatly neglected, but are sufficiently worthy of attention ; copper is found in a native state, and under the form of vitreous and oxidulated copper in several mines ; and, from the quantity of instruments of that metal found among the ancient Mexicans, must be plentiful in the country. About 1565 quintals of plate copper, and 13,947 lbs. of wrought copper, amounting altoge ther to the value of 42,131 piastres, were exported from Mexico in 1802. Tin is found in veins, but is extract ed chiefly from the earth of alluvial lands brought down the ravines ; and about quintals were exported in 1803, to the value of 1,483 piastres. Iron, though little used by the ancient Mexicans, is more abundant than is generally believed, and particularly in the provincias in ternas ; but is wrought with any degree of spirit only when a maritime war has interrupted the importation of steel and iron from Europe. Lead is very abundant in various parts of New Spain, but the mines are not wrought to any extent ; and only 330 quintals were exported in 1802, besides what is required in the country. 11Iercury might be procured in considerable quantities from the numerous veins of Cinnebar which are found in Mexi co; and, instead of being received, may one day be sup plied by America ; but at present 16,000 quintals are annually imported for the mining operations of New Spain. Zinc, antimony, and arsenic are found in se veral places, but cobalt has not been discovered among the minerals of the country ; and manganese is less abundant than in the corresponding latitudes of the old. continent.
Coal also is very rare, and is most abundant to the west of Sierra Verde near the lake of Timpanogos. Rock salt is found in the same place ; and soda is merely disseminated in the argillaceous lands, which cover the ridge of the Cordilleras. The most abundant salt mine in Mexico is the lake of Penon Blanco, in the intendan cy of San Luis Potosi, the bottom of which is a bed of argil, yielding 12 or 13 per cent. of muriate of soda ;
but. as the Indians, who form the great part of the po pulation, continue to season their food with pimento instead of salt, the consumption of these articles in Mexico is chiefly confined to the amalgamation of silver minerals, for which purpose from 20 to 30 fanegos are annually imported from Europe.
All the metallic wealth of New Spain, as well as in the other colonies, is in the hands of individuals ; and the government is not even proprietor of the great levels. Individuals receive from the king a grant of a certain number of measures in the direction of a vein or bed ; and are bound in return to pay very moderate duties on the minerals extracted from the mines, amounting in general to about 13 per cent. The num ber of persons employed in these subterraneous opera tions, throughout the whole of New Spain, does not exceed 30,000, which is only about as of the whole population. The labour of a miner is entirely free ; and no Indian or Mestizoe can be compelled to engage in the working of mines, or to continue in one place when he is thus employed. No miners arc better paid than those of Mexico; and no where do they enjoy in greater security the fruit of their labours. Nor is their occupation observed to be more destructive of health than that of the other classes, although their exertions are great. and the temperature in which they exist very high. In several of the mines the heat is eleven de grees of Fahrenheit ahovc the mean temperatures of Jamaica and Pondicherry ; and the labourers, who carry the minerals on their backs, are exposed to a change of temperature, in ascending and descending, of more than 40 degrees. Vet, in these circumstances, they will re main for six hours under a load of 225 or 350 pounds, ascending eight or ten times successively stairs of 1800 steps. But this labour is accounted unhealthy, if they enter the mines above three days in the week. Those who blow the rock with powder, are found to suffer most in their health ; and hence they seldom continue more than five or six years at this employment. They arc well paid in every department of the work ; and ge nerally gain from 20 to 24 shillings per week, while la bourers in the open air can earn only from six shillings and three-pence to seven shillings and sixpence in the same space of time. They are, nevertheless, much ad dicted to pilfering ; and, though almost naked, contrive a number of plans to secrete the richer minerals,con cealing them in their hair, their mouths, under their arm-pits, and sometimes even inserting them by means of cylinders of clay into their anus. They are of conse quence regularly searched upon leaving the pit ; and a register kept of the minerals detected about their per sons, which, in one valuable mine, has been known to amount nearly to 30001. per annum.