North and South America for metallurgical treatment, and another portion to the improved processes of extraction. The product from German ores is probably not more than $3,000,000. France is not a silver-ore producing country; but the separation of silver from argentiferous lead ores is carried on to a considerable extent. In 1865 it produced 31,997 kilos of silver, worth $1,414,000; in 1869 (the year before the war), 46,299 kilos, worth $2,020,000. No Spanish silver mines were specially important after the middle ages down to 1825, except those of Guadalcanal and Cazalla, N. E. of Seville, which were profitably worked by the government in the 16th century, producing altogether 400,223 marks of silver; afterward they passed into private hands, and in the beginning of the 17th century are said to have produced 170 marks daily, They were finally abandoned, and allowed to fill with water. In 1825 mining was revived in Spain; in 1839 the famous silver mines of the Sierra Almagrera (N. and S. veins in slate, carrying argentiferous galena, with some silver chloride), in the province of Almeria, were discovered, and in 1843 those of Hiendelaencina (narrow E. and W. veins of silver sulphide and chloride, without lead), in the province of Guadalajara. The Herminia mine, in the Sierra Almagrera, in 1874 produced 18,940 quintals of ore, containing 342,325 lbs. of lead and 41,670 Spanish oz. (3,205 lbs. roy) of silver. The product of the mine in the early part of 1875 was at the rate of about 10,000 lbs. troy per annum. The average value of the work lead is about 20 oz. troy per ton avoirdupois. The product of the mines of Hiendelaencina from January, 1847, to July, 1866, was 7,578,536 oz. troy. They have declined in yield since 1858. By the application of the Pattinson process to the argentiferous galenas of the numerous lead mines of Spain, the production of silver has been increased, The export of lead in 1874 was 86,802,271 kilos, valued at 47,034,022 pesetas. This indicates a value of about $1,700,000 for the silver in the lead. The product of Russia in 1871, from 21 mines of argentiferous galena, was 1,740 tons of lead and 29,000 lbs. of silver.—The conquest of Mexico by Cortes in 1519-'21 was soon followed by the development of the wonderfully rich silver mines of that country. The metal was known to the ancient Aztecs, and was worked by them into numerous ornamental and useful articles; but among the treasures of Montezuma the quantity of silver was small compared with that of gold, and gave little promise of the unbounded resources of the argentiferous mines of his territories. During the 16th century these were opened and extensively worked by the Spaniards in Guanajuato, Zacatecas, and other neighboring districts; and in the 17th and 18th centuries their production was greatly increased by reason of the greater abundance of quicksilver and its more general employment in separating the metal from its ores. At the time of the visit of Humboldt operations were carried on in from 4,000 to 5,000 localities, which might all be included in about 3,000 distinct mines. These were scattered along the range of the Cordilleras in eight groups, the principal of which, known as the central group, contained the famous mining districts of Guanajuato, Catorce, Zacatecas, and Sombrerete, and furnished more than half of all the silver produced in Mexico. The mines of Guanajuato, opened in 1558, are all upon the great vein, known as the veta madre, in the range of porphyritic hills the summits of which are from 9,000 to 9,500 ft. above the sea, but only about 3,000 ft. above the high plateau of central Mexico upon which they stand. The great vein is contained chiefly in clay slate, and crosses the southern slope of the hills in a N. W. and S. E. direction, dipping with the slates (the range of which it follows) from 45° to 48° toward the S. W. It is of extraordinary thickness, often more than 150 ft. across, and is said to have been traced for about 12 m.; but the productive portions are chiefly upon a length of about 1¼ m. The vein is made up of quartz, carbonate of lime, fragments of clay slate, together with large quantities of iron pyrites, and sulphurets of lead and zinc with some native silver, sulphuret of silver, and red silver. Near the surface they are partially decomposed and colored red, whence they are termed colorados. In their unchanged condition below they are designated negros or black ores. These are the main dependence of the mines. The vein has been penetrated to the depth of about 2,000 ft., but not much below the level of the plateau. For the two years ending in July, 1873, 115 mines in this district produced 202,125 kilos of silver ($8,045,425), 36 haciendas and zangerros being employed in reduction. In 1873 the number of miners and laborers was 8,979, and the amount of ore raised was 1,815 tons weekly; average contents of silver, about 34 oz. troy to the ton avoirdupois. The mine of Valenciana, opened in 1760, upon a rich portion of the vein, averaged for many years a product of $1,600,000, or about 115 of the total product of the 3,000 mines of Mexico, and a quarter of that of the whole of the veta madre. It declined in productiveness at the beginning of this century, was suspended in 1810 on account of the war of independence, reopened in 1822 by the Anglo-Mexican company, and abandoned after much expenditure to the Mexican owners. It is the deepest mine in the country, and the lower workings are now flooded. In 1873 it employed 1,950 laborers, and yielded about 195 tons of ore weekly. The mines of Zacatecas, opened in 1548, are also upon a single vein called the veta grande, averaging in thickness about 30 ft. The formation is of greenstone and clay slate, the former the most productive. The veins of Catorce are in limestone supposed to be of carboniferous age. The
