All along the eastern part of the plateau from Lake Titicaca to the southern boundary, tin is found in thick unbroken lodes. The three principal districts are La Paz, Oruro, Potosí. In La Paz the best known mines are on the slopes of the splendid mountain, Huaina Potosí in the Cordillera Real, though many other mines are worked. Those in the Department of Oruro are more important, producing one-third of the output. The lodes vary in thickness from a few inches to 10, 15, or 20 feet. Rich pockets are found 30-60 feet in diameter, and veins with stannic oxide fragments, running from 50 to 100 per cent. Cassiterite, tin stone, or tin with stannic oxide, is frequent with 55-60 per cent tin; this is sent to Europe as extracted. The percentage of tin in a lode is very variable, often 6-8 per cent, sometimes 15. Veins of tin on the Cerro Potosí penetrate the hill parallel to veins of silver; some are united; in others tin, silver, and copper alternate or are in union. The tin is generally in the upper part nearer the surface. Sulphides are found at Oruro, but oxides are more frequent. All are at an altitude of about 10,000-17,000 feet. The large Socavón Company employs 1000 hands, has a concentrating plant, and puts out six tons of silver and 250 tons of tin yearly. Many other mines export barilla, some of it with 70 per cent of tin. A Bolivian, Simon J. Patiño, from being an ordinary laborer has risen to be the Tin King, both banker and mine owner, working his mines by modern methods and electric machinery. His mines at Uncia are among the richest in the world, producing about 30 per cent of the Bolivian total. The Llallagua mines, the richest of all, have still greater production. On Huaina Potosí are placers containing with tin, gold in flakes, bismuth, and oxide of iron; more in other locations. The Company owning the Chlorolque Mountain and other properties, with tin as the principal product, mines also silver, bismuth, copper, and wolfram; it paid a 30 per cent dividend in 1917. Capital only is needed to exploit on a much larger scale these rich and available deposits. Three hundred to four hundred dollars a ton hardly paid the cost of production, but with prices three times as much it is a highly profitable business. The Guggenheims have recently purchased three tin mines located at Caracoles on the Quimsa Cruz Range, south of Illimani, to which they have built an automobile road 150 miles from Eucalyptus, a station on the main line between La Paz and Oruro. The mines are at an altitude of 16,000 to 18,000 feet, the quarters at 15,000 to 16,000. The tin runs to 10-15 per cent. It is thought that the property will rival the Uncia. The International Mining Company has a tin property in the Yungas Province 52 miles from La Paz at a height of 8000 feet, a rather more comfortable altitude.