In

those of the mine of Conception, are of a tile-red colour, and mixed with muriate of silver. general it is observed both in Mexico and Peru, that those oxidated masses of iron which contain silver, are peculiar to that part of the veins nearest to the surface of the earth. The pacos of Peru present to the eye of the geologist a very striking analogy with the earthy masses called by the miners in Germany the iron hat (eiserne huth) of the veins*.

Native silver, which is much less abundant in America than is generally supposed, has been found in considerable masses, sometimes weighing more than 440lbs. avoird., in the mines of Batopilas in New Biscay. Native silver is constantly accompanied by glaserz in the veins of Mexico, as well as in those of the mountains of Europe. These very minerals are frequently found united in the rich mines of Sombrerete, Madroño, Ramos, Zacatecas, Hapujaha and Sierra de Penos. From time to time small branches or cylindrical filaments of native silver are also discovered in the celebrated vein of Guanaxuato; but these masses have never been so considerable as those which

*The ochreous mixtures here described as common in Mexico, Peru and Germany, answer so exactly to the gossans of Cornwall that there is no doubt of their being the same; and we have at the mines of Wheal Duchy and Wheal St. Vincent in Calstock in that county, instances of gossan rich in silver, and similar in most respects to the pacos and colorados above mentioned.-J. T.

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were formerly drawn from the mine del Encino near Pachuca and Tasco, where native silver is sometimes contained in foliated gypsum. At Sierra de Penos near Zacatecas, this metal is constantly accompanied with blue radiated copper crystallized in small four-sided prisms.

A great part of the silver annually produced in Europe, is derived from the argentiferous sulphuret of lead. In Mexico, the greatest part of the veins contain likewise some argentiferous galena; but there are very few mines in which the lead ore is a particular object of their operations. Among the latter, we can only include the mines of the districts of Zimapan, Parral, and San Nicholas de Croix. I observed that at Guanaxuato, as well as several other mines in Mexico*, and every where in Saxony, the varieties of galena contain the more silver, the finer they are in the grain.

A very considerable quantity of silver is produced from the smelting of iron pyrites (mundic), of which New Spain sometimes exhibits several varieties richer than the glaserz itself. It has been found in the Real del Monte, on the vein of Biscaina, near the pit of San Pedro, the ton of which contained

* Among the varieties of galena, particularly rich in silver, and of very fine grain, may be specified those of the new mine of Talpan, in the Cerro de las Vegas, belonging to the district of Hostotipaquillo. This galena, which sometimes passes into compact antimonial sulphuret of lead, is accompanied with much copper pyrites and carbonate of lime.

even so much as 450oz. troy of silver. At Sombrerete, the abundance of pyrites disseminated in the red silver ore, is a great obstacle to the process of amalgamation.

We have described the ores which produce the Mexican silver, and it remains for us to examine into the mean riches of these minerals, considering them as all mixed together. It is a very common prejudice in Europe, that great masses of native silver are extremely common in Mexico and Peru, and that in general the mineralized silver ores destined to amalgamation or smelting, contain more ounces of silver to the ton, than the poor ores of Saxony and Hungary. Full of this prejudice, I was doubly surprised, on my arrival in the Cordilleras, to find that the number of poor mines greatly surpasses those of the mines to which in Europe we give the name of rich. A traveller who visits the famous mine of Valenciana in Mexico, after having examined the metalliferous repositories of Clausthal, Freiberg, and Schemnitz, can scarcely conceive how a vein, which for a great part of its extent contains the sulphuret of silver disseminated in the lode in almost imperceptible particles, can regularly supply 230,000oz. per month, a quantity of silver equal to the half of what is annually furnished by all the mines of Saxony. It is no doubt true that blocks of native silver (papas de plata) of an enormous weight, have been extracted from the mines of Batopilas in Mexico and Guantahajo in Peru; but

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when we study attentively the history of the principal mines of Europe, we find that the veins of Kongsberg in Norway, Schneeberg in Saxony, and the famous metallic repository of Schlangenberg in Siberia, have produced masses of much more considerable bulk. We are not in general to judge from the size of the blocks, of the wealth of the mines of different countries. France does not altogether produce more than 5000lbs. troy of silver annually; and yet there are veins in that country (those of Sainte-Marie-aux-Mines) from which amorphous masses of native silver have been extracted, of the weight of 66lbs. avoird.

It appears that at the period of the formation of veins in every climate, the distribution of silver has been very unequal; sometimes concentrated in one point, and at other times disseminated in the lode, and allied with other metals. Sometimes in the midst of the poorest ores we find very considerable masses of native silver; a phenomenon which appears to depend on a particular operation of chemical affinities, of whose mode of action and laws we are completely ignorant. The silver, instead of being concealed in galena, or in pyrites in a small degree argentiferous, or of being distributed throughout all the mass of the vein over a great extent, is collected into a single mass. In that case the riches of a point may be considered as the principal cause of the poverty of the neighbouring ores; and hence we may conceive why the

richest parts of a vein are found separated from one another by portions of the lode almost altogether destitute of metals.

Although the New Continent, however, has not hitherto exhibited native silver in such considerable blocks as the Old, this metal is found more abundantly in a state of perfect purity in Peru and Mexico, than in any other quarter of the globe. In laying down this opinion, I am not considering the native silver which appears in the form of lamellæ, branches, or cylindrical filaments, in the mines of Guantahajo, Potosi, and Gualgayoc, or in Batopilas, Zacatecas, and Ramos. I found my opinion rather on the enormous abundance of the ores called pacos and

colorados, in which silver is not mineralized, but dissemimated in such small particles, that they can only be perceived by means of a microscope*.

The result of the investigations made by Don Fausto d'Elhuyar, the director general of the mines of Mexico, and by several members of the superior council of mines, is, that in uniting together all the silver minerals annually extracted, it would be found

*The most considerable copper mines of England have always owed their importance more to the quantity than the quality of their ores, and experienced men know that it is but delusive to depend upon rich specimens.

Where profit is, however, to be derived by working mines which yield their produce in a disseminated state, the value of good management, and of the application of machinery, becomes the more important, and the results have often proved the most beneficial.-J. T.