[Footnote 26: The gross amount of this production of silver, on the data in the text, is 11,648,000 ounces yearly; worth, at 5s. 6d. per ounce, L. 3,203,200 sterling; and, estimating silver in those days, at six times its present efficacy, worth L. 19,219,200 of modern value. In the present day before the revolutionary troubles, Humboldt estimates the entire production of gold and silver from Spanish and Portuguese America at L. 9,787,500; only about three times the quantity said to have been at first extracted from Potosi alone, and only about half the effective value.--E.] These rich mines are known by the name of Potosi, which is that of the district, or province in which the mountain is situated. Owing to the easy labour and great profit experienced by the Indians at these mines, when any of the Yanaconas was once established at this place it was found almost impossible to induce them to leave it or to work elsewhere; and indeed, they were here so entirely concealed from all dangers, and so much exempted from their usual severe drudgery and the unwholesome vapours they had been subjected to in other mines, that they preferred working at Potosi to any other situation. So great was the concourse of inhabitants to Potosi, and the consequent demand for provisions, _that the sack of maize was sold for twenty crowns, the sack of wheat for forty, and a small bag of _coca_ for thirty dollars; and these articles rose afterwards to a higher price. Owing to the astonishing productiveness of these new mines, all the others in that part of Peru were speedily abandoned. Even those of Porco, whence Ferdinand Pizarro had formerly procured great riches, were left unwrought. All the Yanaconas who had been employed in searching for gold in the province of Carabaya, and in the auriferous rivers in different parts of southern Peru, flocked to Potosi, where they were able to make vastly more profit by their labour than in any other place. From various indications, those who are most experienced in mining believe that Potosi will always continue productive and cannot be easily exhausted[27]. [Footnote 27: It has however become very much exhausted, and has been in a great measure abandoned. The mines of Lauricocha, in a different part of Peru, are now in greater estimation. But those of Guanaxuato and Zacatecas in Mexico, notwithstanding the poverty of their ore, have been long the most productive of the American mines.--E.]