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IV. the number of piastres coined from the silver of Potosi..
The following table exhibits the state of these mines from the period when the fifths : were recorded with accuracy.
Mines of the Cerro de Potosi (Hatun-Po
Marcs of silver extract
ed from the mines. Produce in a Piastres. es. Supposing Supposing
the piastre the piastre at 134 reals. at 8 reals,
From 1556 to 15662,159,216 428,767 -
1585 15957,540,6201,497,380 887,073 1624 16345,232,425 - - 1615,580 1670 1690 3,234,580 - - 380,538 1720 1730 1,299,8001
152,918 1740 1750 1,850,250 - - 217,676 1779 1789 3,676,3301 - 432,5101
As there is some uncertainty respecting the period at which they ceased to reckon by piastres of 13 reals, of which 5, make a marc of silver, I prefer giving both valuations of the piastres till 1595; and we thus obtain the maximum of 'wealth which we are at liberty to suppose. A passage of the commentaries of Garcilasso, already quoted by us, would lead one to believe, however, that a few years after 1580, they reckoned at Peru by piastres of 8 reals de plata. During the whole period of 233 years, from 1556 to 1789 the mining of Potosi never attained so high a degree of splendour as from 1585 to 1606. For several consecutive years the fifth was a million and a half of piastres, which supposes a produce of 1,490,000, or 882,000 marcs according as we value the piastre at 131 or 8 reals. This wealth is the more surprising, as according to Acosta, more than a third of the silver was never registered. After 1606 the produce has been gradually diminishing, and especially, since 1694. From 1606 to 1688 however, it was never below 350,000 marcs. During the last half of the 18th century the mountain generally supplied from three to four hundred thousand marcs; and this produce is undoubtedly still too considerable to allow us to advance with a celebrated author* that the mines of Potosi are no longer worth the trouble of working. These mines in their present state are not the first in the known world; but we may rank them immediately after the mines of Guanaxuato.
The contents of the minerals of Potosi
* Robertson's History of America, b. iv. p. 339 and 399. have diminished in proportion to the increase of the works in depth. In this point of view, and in many others besides, the Cerro de Potosi bears a great analogy to the mines of Gualgayoc. At the surface of the earth, the veins of Rica, Centenó and Mendiata, which traverse primitive slate were full, throughout their whole extent (puissance) of a mixture of sulphuretted, red, and native silver. These metallic masses rose in the form of crests (crestones), the rocks of the wall and roof having been destroyed either by the action of water, or by some other cause which has changed the surface of the globe. The Veta del Estaño on the other hand, contained at its surface only sulphuretted tin, and the minerals of muriated silver only began to appear at great depths*. This mixture of two formations on one vein, exists also in the Old Continent, for example, in several mines of Freiberg in Saxonyt. In 1545 minerals containing from 80 to 90 mares per quintal were very common; but we must not admit with Ulloa that the whole volume of minerals extracted from the mine, amounted to this degree of wealth. Acosta says expressly that in 1574 the mean contents were from 8 to 9 marcs, and that the minerals which
yielded 50 marcs per quintal were considered extremely rich. Moreover according to the report of Don Francisco Texada on the minés of Gaudalcanal in Spain, in 1607 the mean wealth of the minerals of Potosi was not above an ounce and a half. Since the commencement of the 18th century, they reckon only from 3 to 4 marcs per caxon of 5000 pounds, or from 180 to 64. per quintal. The minerals of Potosi are consequently extremely poor, and it is on account of their abundance alone, that the works are still in such a flourishing state. · It is surprising to see that from 1574 to 1789, the mean riches of the minerals have diminished in the proportion of 170 to 1, while the quantity of silver extracted from the mines of Potosi, has only diminished in the propor. tion of 4 to 1.
From 1545 till 1571 the silver minerals of Potosi were all smelted. The knowledge of the con. quistadores being confined to military affairs, they were unacquainted with the carrying on of metallurgical processes. They did not smelt the mineral by means of bellows, but they adopted the whimsical method employed by the Indians in the neighbouring mines of Potosi, which had been wrought on account of the Inca, long before the conquest. They established on the mountains which surround the town of Potosi, wherever the wind blew with impetuosity, portable furnaces, called huayres or guayaras in the Quichua language. These furnaces were cylindrical tubes of clay, very broad, and pierced with a great number of holes. The Indians threw in bed by bed silver mineral, galena, and coal; and the current of air which entered at the holes into the interior of the huayre quickened the flame, and gave it a great intensity. When they perceived that the wind blew too strong, and that too much fuel was consumed, they carried their furnaces to a lower situation. The first travellers who visited the Cordilleras, all speak with enthusiasm of the impression made on them by the first appearance of more than 6000 fires, which illuminated the summits of the mountains round the town of Potosi. The Indians extracted the galena necessary for their smelting, from a smaller mountain, in the vicinity of the Cerro de Hatun-Potocsi called the child, or Huayna Potocsi*. The argentiferous masses which
* Properly the Father mountain and the son-mountain. The different summits of the Volcan de Pichincha, bear analogous denominations; and it is because the French academicians have not distinguished in their works the old Rucu-Pichincha from the young, or Guagua-Pichincha, that it is so difficult to find the place of the academical station of Bouguer, La Condamine, and d'Ulloa. (See my Recueil d'Observations Astronomiques. vol. i. p. 308.)