is a precious metal of a bright yellow color, the most ductile and malleable of all the metals (See DUCTILITY; MALLEABILITY). It may be beaten into leaves so exceedingly thin that one grain in weight will cover 56 square inches, and it will take 280,000 such leaves to make an inch in thickness. A single grain may be drawn into a wire 500 feet long, and an ounce of gold can be made to cover a tiny silver wire more than 1300 miles in length. It may also be melted and remelted with scarcely any diminution of its quantity. It is soluble in nitro-muriatic acid, or aqua regia, and in a solution of chlorine, but it does not tarnish on exposure to the air. It is one of the heaviest metals, being about nineteen and one-third times heavier than water. The fineness of gold is estimated by carats, pure gold being twenty-four carats fine. Jeweler's gold is usually a mixture of gold and copper in the proportion of three-fourths of pure gold to one-fourth of copper. Gold is seldom used for any purpose in a state of perfect purity, on account of its softness, but is combined with some other metal to render it harder. Standard gold, or the alloy used for the gold coinage, consists of twenty-two parts of gold and two of copper and is therefore called twenty-two carats fine. Articles of jewelry in gold are made of every degree of fineness up to eighteen carats, that is, eighteen parts gold to six parts alloy. The alloy of gold and silver is found already formed in nature. It is distinguishable from that of copper by its pale yellow color, the copper, alloy having a color bordering upon reddish-yellow. Palladium, rhodium and tellurium are also met with as alloys of gold. Gold has been found in smaller or larger quantities in nearly all parts of the world. It is commonly found in reefs, or veins, amid quartz, and in sand and gravel; it is separated, in the former case, by quarrying, crushing, washing and treatment with mercury. The rock is crushed by machinery and then treated with mercury, which dissolves the gold forming a liquid amalgam. The mercury is then distilled, and the gold is left behind. According to another method the crushed ore is fused with metallic lead, which dissolves out the gold, the lead being afterward separated by placing the alloy in a porous cup and heating. The lead melts at a lower temperature than the gold and is absorbed by the cup, leaving the gold free. This process is called cupellation. Gold is extracted from sand and gravel by washing and is obtained in the form of dust, grains and nuggets. In modern times large supplies of gold were obtained from Peru, Bolivia and other new countries. Till the discovery of gold in California, a chief source of the supply was the Ural Mountains, in Russia. An immense increase in the total production of gold throughout the world was caused by the discovery of gold in California in 1848, and the opening of the equally rich gold fields of Australia in 1851. Latterly the yield from both sources has considerably decreased. Gold mines have also been extensively worked in New Zealand. British Columbia, Vancouver and the Klondike are the chief Canadian gold fields, but the metal is also found in Saskatchewan, Ontario and New Brunswick. In the United States, apart from California, gold in considerable quantities is found in many states and territories, chiefly Colorado, Dakota, Idaho, Montana, Nevada and in Alaska. South Africa has recently taken a conspicuous position as a gold-producing country, the mines of Transvaal Colony being among the most valuable in the world. Natal and New Caledonia have also important gold fields. The annual production of gold for the world amounts to about $450,000,000. Of this Australasia produces about $72,000,000; Africa about $150,000,000, and the United States about $95,000,000.