greatest proportion of silver in every mining district of Mexico is obtained from the sulphuret of silver, an ore of gray color disseminated through the quartz matrix in minute particles and more or less combined with other metals. The other varieties of argentiferous ores are numerous, but comparatively small in quantity; they are the chloride of silver, ruby silver, native silver, argentiferous pyrites, and argentiferous galena. The comparative quantities of these at the different mines are very variable. Until the present century the ores were extracted altogether by the rude methods of the native Indians. They brought them upon their backs up the long flights of thousands of roughly formed steps, in loads of 240 to 380 lbs. each, while exposed all the time to the great heat of the mine. In 1821 the Mexican government offered facilities for foreigners to become interested with the natives in the mines. English mining companies were formed, and operations were undertaken with powerful machinery; but the adventures were almost universally unsuccessful, the nature of the country being extremely unfavorable for the introduction of heavy machines, as well as for keeping them in operation and repair. From the opening of the Mexican mines in the 16th century their production of silver has exceeded that of all other countries. A great stimulus was given to it by the amalgamating process devised by Medina at that early period in Mexico, and it soon attained an annual rate of from $2,000,000 to $3,000,000. This continued to increase till in the 18th century it rose to $23,000,000, which was about the production for the first ten years of the present century. After 1850 it increased, till for some years it exceeded the yield of all past periods. The total product, from the first working of the mines by the Spaniards to their expulsion by the Mexicans in 1821, was $2,368,952,000. A very promising field for silver mining is found in the state of Sinaloa and along the western slope of the Sierra Madre of Durango and Chihuahua. The port of Mazatlan is the base of supplies. Sinaloa is well wooded and watered; the ores are largely true silver ores, which can be treated by the Freiberg or the modified Washoe process. Some of the mines in the interior are exporting rich silver ores to Europe; others are reported to be earning good profits with stamp mills. Central America has no silver mines that are worked to much extent; but rich ores are known to exist in Honduras, Nicaragua, and Costa Rica.—The famous mines of Potosí in Peru (now in Bolivia) were discovered in 1545 by an Indian hunter, Diego Hualca, who, according to Acosta, accidentally exposed native lumps of the precious metal in the roots of a bush which he pulled from the ground. For 20 years succeeding 1557 the annual production of the mines of this region was about $2,200,000, and the total product up to the present time is rated at over $1,300,000,000. The mines, like so many others in Mexico and South America, are now reported to be flooded in their depths. In the Cerro de Fernando at Hualgayoc, near Micuipamba, rich ores were discovered in 1771, and now, it is said, about 1,400 pits are opened in the hill. Other mining districts in Peru are Gualanca in the province of Huamalies, Pasco, Lucanas, and Huantajaya. Cerro de Pasco has been especially famous for its large production. A town is built upon the site of the mines, and the openings to many of them are through the houses of the miners. The production of Peru until within a few years was very small, probably not more than $2,500,000 annually, and it is a very difficult field for mining. Roads, mules, labor, and fuel are all wanting. The ores (except the pacos or ferruginous earths of Cerro de Pasco), being complex sulphurets, are exceedingly refractory. In the absence of better fuel, llama dung is employed for roasting at several establishments. But the country is full of undeveloped veins, and coal has been discovered in abundance, while railroads are rapidly extending into the interior. In Bolivia, besides the mines of Potosí, are those of Portugalete in the province of Chichas, celebrated for the richness of their ores, which produce six to eight times as much silver to the ton as those of Potosí. Other mines are worked in the same district. The mines of Lipes have been very productive, and those also of La Plata, Porco, Carangas, and Oruro. The earlier silver mines worked in Chili were in the province of Santiago and in the mineral district of Arqueros, about 17 leagues from Coquimbo. The production was not large, and almost ceased upon the opening of the rich mines near Copiapó in the province of Atacama. Within a circuit of 25 leagues from this city there are 19 silver-mining districts, of which those of Chañarcillo and Tres Puntas are the most important. The metal is found in a variety of combinations, as a sulphuret, chloride, chlorobromide, and iodide; it is also associated with arsenic, antimony, and mercury, and is sometimes abundant in a native state. The mines are in a country difficult of access, quite unproductive even in the timber and fuel required for mining, almost entirely destitute of water, and cold and dreary. A new and rich district has been developed at Caracoles, where the ores, like most of those of Copiapó, are chlorides, and easy to reduce.—Silver mining in the western United States, apart from the early operations of the Spaniards in New Mexico and perhaps Arizona, dates from the discovery in 1859, on the E. flank of the Sierra Nevada, in the present state of Nevada, of the now famous Comstock lode. (See Nevada.) No equally important argentiferous deposit has since been discovered; and, in view of the most recent exposures of vast bodies of ore at great depth on the Comstock, it may be doubted whether its
