In Chihuahua active development upon copper mines is being carried on, and the production stimulated by the establishing of smelting works. There is also an important copper foundry at Monterrey, in the State of Nuevo Leon. In Lower California are the large copper mines and smelting works of Boleo, owned by a French company. This is an important enterprise, supporting a population of 8,000 souls, and its eight smelters are of a capacity of 150 tons daily, giving an output of copper of 11,500 tons per annum. With its own railways, harbour, and town, the enterprise is a self-centred community of much prosperity. The State of Guerrero affords some copper ore deposits probably of great extent, and among these are several mines which are being developed. In the State of Zacatecas is the important British enterprise of the Mazapil Copper Company, with an extensive property, smelting furnaces, and railway line, with also a long overhead cable system of ore-carriage. _Iron_.--Deposits of iron ores are found in several of the states. In Durango is the much described _Cerro de Mercado_, a hill of iron ore calculated as containing 460,000,000 tons of iron ore, assaying 70 to 75 percent. pure iron. This remarkable hill was discovered in 1552. The city of Monterrey, in the State of Nuevo Leon, contains a large ironfoundry and steel-producing plant, and two iron and brassfoundries, establishments which are of much importance to the country. Guerrero has valuable deposits of iron ore near Chilpancingo. _Quicksilver_.--In the State of Guerrero are the quicksilver mines of Ahuitzuco, which have produced quantities of mercury. Durango has deposits of cinnabar at Nazas and El Oro. _Coal_.--In the State of Sonora are extensive fields of anthracite, with seams in some cases 14 feet in thickness, and these are being developed by an American company. Near these are others, equally important, and the whole area is very considerable. Coahuila contains perhaps the most important coal-beds in the Republic, and a considerable output of coal and coke is being made. Other states contain coal-fields. _Petroleum_.--In the State of Tamaulipas are the petroleum deposits of "El Ebano," worked by an American company. In July, 1908, an enormous "fresher" was struck at San Geronimo, near Tampico, and this became ignited and burned fiercely for two months, with a pillar of flame 1,000 feet high, which was visible for 100 miles. So rapid was the flow of oil when this was extinguished that earthen dams were hastily constructed to save the oil. Several other states have oil deposits. _Salt_.--In Tamaulipas, on the Gulf of Mexico, the salt mines of Matamoros and Soto la Marina produce quantities of salt. On the Pacific side of the country, Carmen Island, off the Gulf coast of Baja, California, exists one of the largest salt-beds in the world.