The two chief forms of power upon which modern industry depends are petroleum and coal. The United States is the largest producer of both of these commodities. The world's production of petroleum in 1917 was 506.7 million barrels (_Mineral Resources_, 1917, Part II, p. 867). Of this amount the United States produced 335.3 million barrels or 66 per cent of the total. The second largest producer, Russia, and the third, Mexico, are credited with 69 million barrels and 55.3 million barrels respectively. As a coal producer the United States stands far ahead of all other nations. The United States Geological Survey (_Special Report_, No. 118) placed the total coal production of the world in 1913 at 1,478 million tons. Of this amount 569.9 million tons (38.5 per cent) were produced in the United States. The production for Great Britain was 321.7 million tons; for Germany 305.7 million tons; for Austria-Hungary 60.6 million tons. No other country reported a production of as much as fifty million tons. In 1915 the United States produced 40.5 per cent of the world's coal; in 1917 44.2 per cent; in 1918 46.2 per cent. Copper has become one of the world's chief metals. Two-thirds of all the copper is produced in the United States. Copper production in 1916 totaled 3,107 million pounds (_Mineral Resources in the United States_, 1916, part I, p. 625). The production for the United States was 1,927.9 million pounds (62 per cent of the whole). The second largest producer, Japan, turned out 179.2 million pounds. The precious metals, gold and silver, are largely produced in the United States. The world's gold production for 1917 was 423.6 million dollars (_Mineral Resources_, 1917, p. 613). Africa produced half of this amount (214.6 million dollars). The United States was second with a production of 83.8 million dollars (20 per cent of the whole). The same publication (p. 615) gives the world's silver production in 1917 as 164 million ounces. 77.1 million ounces (43 per cent) were produced in the United States. The second largest producer was Mexico, 31.2 million ounces; and the third Canada, with 22.3 million ounces. These three North American countries produced 76 per cent of the world's output of silver. Judge Gary, speaking at the Annual Meeting of the Iron and Steel Institute (1920) put the situation in this summary form:-- As frequently stated, notwithstanding the United States has only 6% of the world's population and 7% of the world's land, yet we produce: