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the tenatero, who, during the road has had time to estimate his load, believes it lighter than the despachador, he says nothing, because the error is advantageous to him; but on the other hand, if he believes the weight of the ore he carries in his bag to be greater than it is estimated, he then demands that it should be weighed in the balance; and the weight which is thus determined is entered in the book of the despachador. From whatever part of the mine the tenatero comes, he is paid at the rate of one real de plata for a load of nine arrobas, and one and a half real for a load of thirteen arrobas and a half per journey. There are some tenateros who perform in one day, from eight to ten journies, and their pay is regulated from the book of the despachador. This mode of reckoning is no doubt highly deserving of praise, and we cannot sufficiently admire the celerity, the order, and the silence with which they thus determine the weight of so many thousand quintals of ores, 'which are furnished by veins of twelve or fifteen metres* in breadth in a single day.

These ores, which are separated from the sterile rocks in the mine itself, by the master miners (quebradores) undergo three sorts of preparation, viz. at the place of banes de triage,

* 38 or 48 feet. Trans.

where, women work, under the bocards, and under the tahonas or arastras. These tahonas are machines in which the metalliferous gangue is triturated under very hard stones, which have a rotatory motion, and weigh upwards of seven or eight quintals. They are not yet acquainted with washing with the tub (setz wäsche) nor washing on sleeping tables (tables dormantes) (liegende heerde) or percussion (stossheerde). The preparation under the bocards (mazos) or in the tahonas, to which I shall give the name of mills, on account of their resemblance to some oil and snuff mills, differs according as the ore is destined to be smelted or amalgamated. The mills properly belong only to this last process; however, very rich metallic grains called polvillos, which have passed through the trituration of the tahona are also smelted.

The quantity of silver extracted from the ores by means of mercury, is in the proportion of 34 to 1 of that produced by smelting. This proportion is taken from the general table formed by the provincial treasuries, from the different districts of mines of New Spain. There are, however, some of those districts, for example, those of Sombrerete and Zimapan, in which the produce from smelting exceeds that of amalga-, mation.

Silver (plata quintada) extracted from the mines

of New Spain, from the 1st January, 1785, to the 31st December, 1789.

Silver ex

Silver ex

tracted by tracted by Provincial treasuries receiving amalgamathe fifth.

tion (mar

smelting cos de azo

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I believe we ought to augment the quantities stated in the preceding table one fifth to come at the real state of the mines. In times of peace, amalgamation gains a gradual ascendancy over smelting, which is generally badly managed. As wood is becoming yearly more scarce on the ridge of the Cordilleras, which is

the most populous part, the diminution of the produce of smelting is very advantageous to the manufactories which require a great consumption of combustibles. In times of war the want of mercury arrests the progress of amalgamation and compels the miner to endeavour to improve the process of smelting. M. Velasquez, the director general of the mines, supposed even in 1797, before the discovery of the rich mines of Catorce, where there is scarcely any smelting, that of all the ores of New Spain š were smelted, and the other . amalgamated.

The limits prescribed by us in the execution of this work, do not permit us to enter into any detail of the processes of amalgamation used in Mexico. It may be sufficient to give a general idea of them, to examine the chemical phenomena which are exhibited in the greatest part of these processes, and to show the difficulties which in the New Continent oppose the introduction of the method invented in Germany in 1786, by Born, Ruprecht, and Gellert. Those who may desire to know thoroughly the practice of American amalgamation, will find the most satisfactory information in a work which Mr. Sonneschmidt proposes to publish. This worthy mineralogist resided in New Spain for the space of twelve years; he had occasion to submit a great number of ores to amalgamation; and

he had it in his power to discover by his own experience, the advantages and disadvantages of the different methods which have been followed since the sixteenth century in the mines of America.

The ancients knew the property which mercury possessed of combining with gold; and they made use of amalgamation in gilding copper, and collecting the gold contained in their worn out dresses, by reducing them to ashes in clay vessels. *

It appears even certain that be. fore the discovery of America, the German miners used mercury not only in washing auriferous earths, but also in extracting the gold disseminated in veins t, both in its native state, and mixed with iron pyrites, and with the grey copper ore. But the amalgamation of silver ores, and the ingenious process now used in the New World, to which we owe the greater part of the valuable metals existing in Europe, or which

* Plin. XXXIII. 6. Vetruv. VII. 8. Beckmann's Gesch. der Erfindungen, B. I. p. 44; B. III. p. 307; B. IV. p. 578.

† For example, at Goldcronach, in the Fichtelgebirge, where they still shew the situation of the old amalgamation mills (quickmühlen) for the braying of the auriferous minerals. Valuable documents have been found in the archives of Plasenbourg, which I had occasion to study during a long residence in the mountains of Steeben and Wunsiedel, that prove the antiquity of the amalgamation works at Goldcronach.

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