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The process discovered by Medina possesses the great advantage of simplicity : it requires no construction of edifices, no combustibles, no machines, and almost no impelling force. With mercury and a few mules to move the arastras, we may by means of amalgamation por patio extract the silver from all the meagre ores near the pit from which they are taken in the midst of a desert, provided the surface be sufficiently even to admit of receiving the tortas ; but this same process has also the great disadvantage of being slow and causing an enormous waste of mercury. As the mercury is divided in an extreme degree, and thousands of quintals of minerals are wrought at a time, it is impossible to collect the oxide and muriate of mer cury which are carried away by the water in washing. By the method of amalgamation followed in Europe which we owe to the ingenious researches of M. M. Born, Ruprecht, Gellert, and Charpentier, the silver is extracted in the space of 24 hours ; they employ from sixty to one hundred and fifty times less time than in the Spanish colonies, and consume as we have already said eight times less mercury. But how is there a possibility of introducing into Mexico or Peru, the process of Freiberg, which is founded on the roasting of the ores, and the rotatory motion of the tubs ? At Freiberg, sixty thousand quintals of ores are annually amalga
mated; but in New Spain the quantity is nearly ten millions of quintals, and how is it possible to contain this enormous mass of minerals in tubs ? How can we find sufficient power to turn a million of these casks or tubs ? * How shall we roast the ores of a country which wants combustibles, and where the mines are on table lands destitute of forests ?
After treating of the amalgamation in use in America, it remains for us to touch upon a very important problem, that of the quantity of mercury annually required by the mines of New Spain. Mexico and Peru depend very much upon the abundance and low price of the mercury for the quantity of silver which they produce. When the mercury fails them, which happens often in periods of maritime war, the mines are not so briskly worked ; and the mineral accumulates in their hands without their being able to extract the silver from it.' Rich proprietors, who possess in their magazines ores to the amount of two or three millions of francs, are frequently in want of the necessary money to make head against the daily expenses of their mines. On the other hand the more mer
* It would undoubtedly require a million of casks to receive at once the 17 quintals of minerals ; but supposing that we could amalgamate as rapidly as in Saxony, 3330 tubs would be sufficient to supply the place of the beneficio del patio of all Mexico. Trans.
cury is wanted in Spanish America, either on account of the flourishing state of the mines, or the process of amalgamation followed there, the more the price of this metal rises in Europe. The small number of countries which nature has supplied with it, Spain, the department of Mont-Tonnerre, Carniola, and Transylvania, gain by this rise; but the districts of silver mines in which the process of amalgamation is the more desirable, as they are in want of the necessary combustibles for smelting, feel very disadvantageously the effect of the great importations of mercury
into America. New Spain consumes annually 16,000 quintals of mercury. * The court of Madrid having reserved to itself the exclusive right of selling mercury, both Spanish and foreign, entered in 1784, into a contract with the Emperor of Austria, by which the latter was to furnish mercury at a price of 52 piastres. The court sends annually in time of peace, by vessels of the Royal Navy, sometimes 9000, and some. times 24,000 quintals. In 1803, a very useful project was formed of supplying Mexico for several years, in order that in the unforeseen case of a war, the amalgamation should not be impeded by the want of mercury ; but this pro
ject (del requesto) shared the fate of so many others which have never been executed. Before 1770, when the working of mines was far from being so considerable as at present, New Spain received no other mercury but that of Almaden and Huancavelica. · The German mercury furnished by the Austrian government, of which the greatest part is from Idria, was only introduced into Mexico after the falling in of the subterraneous works of Huancavelica, at a time when the mine of Almaden was inundated in the greatest part of its works", and yielded only a very inconsiderable produce. But in 1800 and 1802, this last mine was again in such a flourishing state, that it could alone have furnished more than 20,000 quintals of mercury per annum, and there were sufficient grounds to conceive the hope of not having any neces. sity of recurring to German mercury, for supplying Mexico and Peru. There have been years, when ten or twelve thousand quintals of this last mentioned mercury, have been imported at Vera Cruz. Upon the whole, from 1762 to 1781, the amalgamation works of New Spain, destroyed the enormous sum of 191,405 quin
* For these mines and those of Almadenejos, see the interesting researches of M. Coquebert de Montbret, in the Journal des Mines, No. 17, p. 396.
tals *, of which the value in America amounted to more than 60 millions of livres tournois. +
When the price of mercury has progressively lowered, the working of the mines has gone on increasing. In 1590, under the Viceroy Don Luis de Velasco II., a quintal of mercury was sold in Mexico for 187 piastres. But in the 18th century, the value of this metal had diminished to such a degree, that in 1750, the court distributed it to the miners at 82 pias. tres. Between 1767 and 1776, its price was 62 piastres the quintal. In 1777, under the administration of the Minister Galvez, a royal decree fixed the price of the mercury of Almaden at 41 piastres, two reals, and that of Germany at 63 piastres. At Guanaxuato, these two sorts of mercury are increased by the ex. pensive carriage on the backs of mules, from 2 to 24 piastres per quintal. The king gains on the mercury of Idria, on account of the difference of the weight used in Germany and in Mexico, 23 per cent. ; so that a wise politician ought to engage the mother country to sell it at a cheaper rate. According to an old custom, the miners of certain districts of mines, for example, those of Guanaxuato and Zacatecas, are allowed to purchase two thirds of
* 25,124,200 lb. Troy. Trans.