Although the expeditions of General Cass in 1819 and of Major Long in 1823 had drawn public attention to the copper of Lake Superior, still twenty years more passed before they became the object of mining speculations, which at once rose to a feverish height. Numerous companies were started in 1843, and mines were opened in many hundred places at once. The natural consequence of this copper mania was disappointment in most cases, and in 1847 the greater number of the mines, which had been opened with the most extravagant expectations, were abandoned. A few companies only withstood the crisis, and ultimately proved so remarkably successful as fully to retrieve the lost credit of the copper country, the annual yield of which at the present time is about 10,000 tons, and consequently nearly equals that of Cornwall. The copper occurs in the native state in veins intersecting the trap and sandstone, but also in scattered superficial masses along the chain of hills which extends from the western to the north-eastern extremity of Lake Superior. In no known locality have such large masses of copper been found. An enormous block was discovered in February 1857 in the Minnesota mine. It was forty-five feet in length, twenty-two feet at the greatest width, and the thickest part was more than eight feet. It contained over ninety per cent. of copper, and weighed about 420 tons. A still more prodigious mass, sixty-five feet long, thirty-two feet broad, and four feet thick, was found in 1869. This king of copper nuggets weighed no less than 1,000 tons, and was worth 80,000_l._, or more than the greatest lump of gold that ever came to light in Australia or California. Rich copper mines have likewise been discovered in the States of Maryland, Pennsylvania, Massachusetts, and New York, but chiefly in California, where since 1861 the small town of Copperopolis[52] has risen into importance. More than 30,000 tons of Californian copper ores (chiefly sulphurets) are now annually exported to the smelting-houses of the bay of Boston, which are likewise supplied by the ores of Chili and Canada, and form a new Swansea on the opposite shore of the Atlantic. The whole annual production of the United States at present exceeds 20,000 tons of metallic copper, mostly consumed in the country. Footnote 52: This hybrid name, a vile compound of English and Greek, is enough to excite the wrath of a philologist. The mines of Cuba, which were very important, have latterly fallen off; but in 1866 the exportation to Swansea still amounted to 11,254 tons of ore.