GRINDING MILL.
The quicksilver being spread over the surface, the mules are once more put in, and tread the whole until it is well mixed. Great skill is now required to watch the progress of the amalgamation, and to decide whether any one of the ingredients that have been added to the ore is in deficiency or excess.
The amalgamating process being at length ended, the mass is washed in large vats, through which streams of water are made to pass, so as to drive away the lighter particles of the mud and to leave the heavy amalgam at the bottom of the tub. After being strained through the strong canvas bottom of a leathern bag, in order to separate the superfluous mercury, the amalgam is finally heated in large retorts, when the quicksilver is volatilised and the pure silver remains behind. As a considerable quantity of mercury is thus lost, this metal has always had a great influence on the working of the Mexican mines. When, in times of war, the importation of quicksilver from Europe was stopped, thus causing a considerable increase in its price, the ores accumulated in the magazines, as their poverty made it impossible to meet the additional expense; and then it not unfrequently happened that proprietors, possessing ores to the amount of several millions of dollars, were unable to pay their current expenses. In the last century, the Mexican mines annually required sixteen thousand hundredweight of mercury, which was furnished chiefly by the mines of Almaden, Huancavelica, and Idria. The sale of mercury to the various mining proprietors was a Government monopoly.
The quantity of silver produced by the Mexican mines in 110 years, ending with the first year of the present century, amounted to about ninety-eight millions of pounds troy, and the total value of the gold and silver produced from 1689 to 1803 to about 285 millions of pounds sterling.
The production was most abundant in the years 1805, 1806, and 1809, when it reached the sum of twenty-six and twenty-seven millions of dollars. It then fell enormously during the revolutionary wars; but the English mining mania of 1824 having furnished the necessary capital for the re-opening of a large number of mines, it again gradually rose, and even reached during some years the rate of its most flourishing period. But it never amounted to one-third of the value which is now annually extracted from our coal mines; and while the latter open new and unbounded sources of wealth by the activity they communicate to numberless branches of industry, Mexico—a prey to bigotry, ignorance, anarchy, and sloth—remains, in spite of her silver mines, as poor and as barbarous as ever.
In South America, the mines of Potosi, Cerro di Pasco, and Gualgayoc, are the most renowned for their richness. In 1545, an Indian, while pursuing some deer along the declivity of a steep mountain, took hold of a shrub, the roots of which, giving way, brought to view a mass of silver, the first discovery of the riches which have rendered Potosi the proverbial symbol of wealth. The Indian, wisely concealing his good fortune, repeatedly visited the mine, but his improved circumstances having been remarked by one of his countrymen, he was obliged to take him into the secret. Unfortunately a quarrel ensued, and the faithless confidant betrayed it to his master, Don José Villaroel, a Spaniard, whose extraordinary success in working the mines soon drew the attention of all America to the wild Cerro di Potosi. A town of 100,000 inhabitants soon rose in the desert, in spite of the wintry inclemency of the climate (12,842 feet above the level of the sea) and of the fabulous prices of provisions, as all the necessaries of life had to be conveyed from a vast distance over the pathless mountains.
But if living in Potosi was extravagantly dear, Mammon took care to provide his votaries with the necessary means; for the treasures which were here extracted from the bosom of the earth seem rather to belong to the world of Oriental romance than to that of sober reality. According to Humboldt, the mountain of Potosi, whose topmost mine is situated 15,384 feet above the level of the sea—considerably higher than the eternal snows of the summit of Mont Blanc—produced from 1545 to 1803 no less than 230,000,000l., besides the silver which was not registered, or had been carried off by fraud, and which may probably have amounted to as much again. During the period of their greatest prosperity—from 1585 to 1606—when they annually yielded 882,000 marks of silver, 15,000 Indians were occupied in the mines of Potosi. At present, however, their produce, though still considerable, has diminished to one-eighth, and the population of the town has shrunk in the same proportion.
The ores were at first reduced in a very imperfect manner, according to the old Indian method. On the mountains surrounding the town of Potosi, wherever the wind blew with sufficient force, portable smelting ovens of clay, in which numerous holes kept up a strong current of air, received alternate layers of ore and charcoal, and the lively blast soon separated the metal from the dross. The first travellers in the Cordillera describe with enthusiasm the magnificent aspect of more than 6,000 fires, which every evening blazed on the mountain crests of Potosi. Amalgamation was first introduced about the year 1571.
On the bleak Puna, or high table-land between the parallel chains of the Cordillera and the Andes, is situated the famous mining town of Pasco. Surrounded by a crescent of steep and naked rocks, its straggling buildings extend over an uneven ground, bordered by small marshes and lagunes. The shivering traveller, descending from the windy heights, is at first agreeably surprised by the sight of a large town in the midst of these dreary solitudes; but a nearer inspection of its narrow crooked streets, and of its miserable huts, with here and there a stately mansion, soon dissipates the fancies he may have formed at a distance.