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The three districts of mines which we have just alluded to, furnish alone, more than a million of marcs of silver, and from the whole of these data we cannot entertain a doubt that the mean contents of the Mexican minerals, do not amount, as we have already stated, to more than from three to four ounces of silver, per quintal. Hence these minerals, though somewhat richer than those of Freiberg, contain much less silver than the minerals of Annaberg, Johann-Georgenstadt, Marienberg, and other districts of the Obergebirge in Saxony. From 1789 to 1799, there have been extracted communibus annis from the seams of the district of Freiberg, 156,752 quintals, which have yielded 48,952 marcs of silver; so that the mean contents were 23: ounces per quintal of minerals. But in the mines of the Obergebirge the mean riches, have amounted to ten, and at very fortunate periods even to fifteen ounces per quintal.
We have taken a general view of the rocks in which the principal mines of New Spain are to be found; we have examined on what points, in what latitudes, and at what elevations above the level of the sea, nature has collected the greatest quantity of metallick wealth; and we have indicated the minerals which furnish the immense quantity of silver which annually flows from the one
continent to the other. It remains for us to afford some details relative to the most considerable mining operations. We shall confine ourselves to three of those groupes of mines which we have already described, to the central gror, e, and those of Tasco and Biscaina. 1 ho, who know the state of mining in Europe will be struck with the contrast between the great mines of Mexico, for example, those of Valenciana, Rayas, and Tereros, and the mines which are considered as very rich in Saxony, the Harz, and Hungary. Could the latter be transported to the midst of the great works of Guanaxuato, Catorce, or the Real del Monte, their wealth, and the quantity of their produce,
would appear as insignificant to the inhabit· ants of America, as the height of the Pyrenees compared with the Cordilleras.
The Central group of the mines' of New Spain, a portion of ground abounding more in silver than any other known on the globe, is situated in the same parallel with Bengal, under a latitude where the equinoctial is confounded with the temperate zone. This group comprehends the three districts of the mines of Guanaxuato, Catorce, and Zacatecas, the first of which possesses an extent of 220, the second of 750, and the third of 730 square leagues, calculating the surfaces from the po
sition of the insulated mines (realitos) at the greatest distance from the chief place of the district.
. The district of Guanaxuato, the most southern of this group, is as remarkable for its natural wealth as for the gigantic labours of man in the bowels of the mountains. To form a more exact idea of the position of these mines, we invite the reader to call to mind what we have already stated * in the particular description of the provinces, and to cast his eyes over the physical section of the central table land, in the atlas to this work. :
In the centre of the intendancy of Guanaxuato on the ridge of the cordillera of Anahuac, rises a group of porphyritic summits known by the name of the Sierra de Santa Rosa.
This group of mountains partly arid, and partly covered with strawberry-trees, and evergreen oaks, is surrounded with fertile and well cultivated fields. To the north of the Sierra, the Llanos of San Felipe, extend as far as the eye
. * Vol. ii. p. 204. I have drawn up a geographical map of the environs of the town of Guanaxuato, which will appear in the historical account of my travels in the Equinoctial Regions of America. This map is partly taken from the perpendicular bases measured barometrically. See Vol. i. Introduction, p. xiii, and my Recueil d'Observations Astronomiques, Vol. i. p. 372.
can reach; and to the South, the plains of Irapuato and Salamanca, exhibit the delightful spectacle of a rich and populous country. The Cierro de los Llanitos, and the Puerto de Santa Rosa, are the most elevated summits of this group of mountains. Their absolute height is from 2,800 to 2,900 metres *, but as the neighbouring plains which are part of the great central table land of Mexico, are more than 1800 metres † above the level of the sea, these porphyritic summits appear but as inconsiderable hills to the eyes of a traveller accustomed to the striking appearance of the Cordilleras. The famous vein of Guanaxuato, which has alone, since the end of the sixteenth century, produced a mass of silver equal to fourteen hundred millions of francs 1, crosses the southern slope of the Sierra de Santa Rosa.
In going from Salamanca to Burras and Temascntio, we perceive a chain of mountains, bounding the plains which stretch from the South-east to the North-west. The crest of the vein follows this direction. At the foot of the Sierra, after passing the farm of Xalapita, we discover a narrow ravin dangerous to pass, at the period of the great
* From 8985 to 9313 feet. Trans.
swells called the Cañada de Marfil, which leads to the town of Guanaxuato. The population of that town, as we have already ob- , served, is more than 70,000 souls. One is astonished to see in this wild spot, large and beautiful edifices in the midst of miserable Indian huts. The house of Colonel Don Diego Rul, who is one of the proprietors of the mine of Valenciana, would be an ornament to the finest streets of Paris and Naples. It is fronted with columns of the Ionic order, and the architecture is simple and remarkable for great purity of style. The erection of this edifice, which is almost uninhabited, cost more than 800,000 francs *, a considerable sum in a country where the price of labour and materials are very moderate.
The name of Guanaxuato is scarcely known in Europe; and yet the riches of the mines of this district is much superior to that of the metalliferous depository of Potosi. The latter was discovered in 1545 by Diego Hualca an Indian, and has produced according to information *
* £33,000, Sterl. Trans. + Extract from a book of accounts of the Royal Treasury of Potosi, made on the spot, by Mr. Frederic Mothes (Razon de los reales derechos que se han cobrado en las cazas reales, de la plata que ha producido el Cerro de Potosi). This manuscript memoir in my possession gives the produce of Potosi every year from 1558 to 1789. The treasury books contain no information relative to the years anterior to 1556, although two miners of Porco, Juan de Villaroel and Diego Centeno, began to work this vein in the year 1545.