The result of this table is, that the silver extracted from the vein of Guanaxuato, contains from one to three thousand parts of its weight in gold.

Platina is erroneously stated to be found in the auriferous sands of Sonora. This metal has never yet been discovered to the north of the Isthmus of Panama, on the Continent of North America. Platina in grains is only found in two places of the known world; in Choco one of the provinces of the kingdom of New Granada, and near the shores of the South Sea, in the province of Barbacoas, between the 2o and 6° of north latitude. It is peculiar to alluvious grounds of a surface of 600 square leagues, the extent of which is scarcely equal to two of the departments of France. The Lavaderos, which at present yield the greatest quantity of platina, are those of Condoto, Santa Rita, or Viroviro, and Santa Lucia, and the Ravin (quebrada) of Iro, between the villages of Novita and Taddo. There are several lavaderos in Choco, (for instance, those of the districts of San Augustin, and Guaicama,) where no trace of platina is to be found. The price of this metal in grain on the spot is eight piastres, or 40 francs the pound, while at Paris it is generally from 130 to 150 francs. I shall examine in another place the quantity of platina, which in the present state of the mines of Choco, Ame

rica can furnish to Europe. It is also an absolutely false assertion, that platina has ever been found near Carthagena or Santa Fe, at the Islands of Porto Rico and Barbadoes, and in Peru*, although their different situations are pointed out in the most esteemed and popular works. Perhaps it will one day be proved by chemical analysis, that platina exists in several silver ores of Mexico, as it exists in the fahlerz (grey-copper) of Guadalcanal in Spain.

The silver supplied by the veins of Mexico, is extracted from a great variety of minerals, which from the nature of their mixture, bear an analogy to those of Saxony, the Harz, and Hungary. The traveller must not expect to find a complete collection of these ores, in the school of mines of Mexico. The mines being all in the hands of individuals, and the Mexican government possessing but a very feeble influence on the administration of the mines, it was not in

* Hauy Mineralogie, T. iii. p. 370. In a memoir inserted in the Annales de Ciencias Naturales, published by the Abbe Cavanilles, we read that platina is found in Chopo, (Choco) at Barbados, (Barbacoas) and at Carthagena a sea port, a hundred and thirty leagues distant from the gold lavaderos of Taddo. Yet more than 18 years ago, M. Berthollet communicated a very accurate account of the places where platina is procured (Annales de Chimie, Juillet 1792) I brought to Europe a pepita of platina of an extraordinary size. It weighs 1088 grains; and its specific weight is according to M. Tralles, 18,947. (Karsten, Min. Tabellen, 1808, p. 96.)

the power of the professors to collect whatever had any relation to the structure of veins, beds, and masses of ore. At Mexico as well as Madrid, the public collections contain the rarest minerals of Siberia and Scotland, while we vainly seek what might throw light on the mineralogical geography of the country. We must hope that the cabinet of the school of mines will become gradually richer, when the scholars of this fine establishment shall be sent into the most distant provinces from the capital, and have proved to the proprietors of mines how much it is for their interest, that the means of instruction should be facilitated. Without a knowledge of the localities in detail, and without a deep study of the minerals of which the mass of the vein, or the contents of the heaps and beds are composed, all the changes which may be proposed for the improvement of the process of amalgamation, will turn out mere chimerical projects.

In Peru, the greatest part of the silver extracted from the bowels of the earth, is furnished by the pacos, a sort of ores of an earthy appearance, which M. Klaproth was so good as to analyse at my request*, and which consist of a mixture of almost imperceptible parcels of native silver, with the brown oxyde of iron.

Klaproth, Beiträge zur chemischen Kenntniss der Mineral -Körper, B. iv. § 4.

In Mexico on the other hand, the greatest quantity of silver annually brought into circulation, is derived from those ores which the Saxon miner calls by the name of dürre erze* especially from sulfuretted silver, (or vitrous glaserz) from arsenical grey-copper (fahlerz) and antimony, (grau or schwarzgiltigerz) from muriated silver, (hornerz)from prismatic black silver,(sprödglaserz), and from red silver (rothgiltigez). We do not name native silver among these ores, because it is not found in sufficient abundance to admit of any very considerable part of the total produce of the mines of New Spain being attributed to it.

Sulfuretted silver, and black prismatic silver, are very common in the veins of Guanaxuato and Zacatecas, as well as in the veta Biscaina of Real del Monte. The silver extracted from the ore of Zacatecas, exhibits the remarkable particularity of not containing gold. The richest fahlore (fahlerz) is that of Sierra de Pinos, and the mines of Ramos. In the latter, the fahlerz is accompanied with glaserz, with pyritous hepatic copper (bunt kupfererz), sulfuretted zinc and vitrous copper (kupferglas,) which is only wrought

* See the very instructive work of M. Daubuisson, under the title of Description des Mines de Freiberg. I have followed in the course of this chapter, in whatever relates to the art of mining, and the stratification of minerals, the terminology of M. M. Brochant, Daubuisson, and Brongniart.

for the extraction of the silver, without applying the copper to any use. The graugiltigerz or grey antimoniated copper described by M. Karsten, is found at Tasco, and in the mine of Rayas, south east from Valenciana. The muriated silver which is so seldom found in the veins of Europe, is very abundant in the mines of Catorce, Fresnillo, and the Cerro San Pedro, near the town of San Luis Potosi. That of Fresnillo is frequently of an olive green, which passes into leek-green (vert poireau). Superb samples of this colour have been found in the mines of Vallorecas, which belong to the district de los Alamos in the intendancy of Sonora. In the veins of Catorce, the muriated silver is accompanied with molybdated lead, (gelb-blei-erz) and phosphated lead (grünblei-erz). From the last analysis of Mr. Klaproth, it appears that the muriated silver of America,* is a pure mixture of silver and muriatic acid, while the Hornerz of Europe contains oxid of iron, alumine, and especially a little sulphuric acid. The mineral of red silver constitutes a

The Mineralogists at present distinguish four kinds of muriated silver, the common, the terreous, the conchoid, and the radiated. The two last species, which are exceedingly beautiful, have been described by M. Karsten: they are among the minerals brought by me from Peru. Karsten, in the Magazine der Berliner Gesellschaft Natürforschender Freunde, B. i. § 156. Klaproth's Beiträge, B. iv. § 10.