Ch. 1: Gold and Silver in 1918

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	744 MINERAL RESOURCES, 1918—PART I,

	tion during the year, these figures record the actual production of gold and silver bullion from domestic ores in marketable form as metals, either refined or unrefined. Owing to the difficulty of tracing this total gold and silver production back to its origin by States, counties, and mining districts, however, the Geological Survey attacks this problem of distribution by systematic investigation of the mine production of ores containing gold and silver during the calendar year and of the output of the placer mines. In this way the state of the mining industry is studied in detail, and the output is classified by methods of production and by kinds of ore, as well as by mining districts. The resulting figures form the basis of the mines reports. Of the two plans outlined for ascertaining the gold and silver production of the United States it may be said that one is a measure of the mining industry and the other a measure of the metallurgic industry; that one reports the mine output and its recoverable content and the other the metal actually recovered in marketable form. The two methods will not produce exactly corresponding results, nor should they be expected to do so. The figures of the reports of the mint and of the mines reports for a period of years sufficiently long to compensate for overlap or lag should agree within allowable limits of error due to the complexity of the problem involved. For the last 14 years in which complete statistics iiave been gathered by both methods the final figures have been as follows:



	These figures show, according to Mint reports, a total excess of gold for the 14 years of $9,346,997, or a difference of about 0.7 per cent, and a total deficit of silver of only 4,100,781 ounces, or a difference less than 0.5 per cent. The figures for Alaska placers are not considered to be so closely approximate as the total figures for gold, hence the differences for the United States proper are probably even lower. It is thought that those small differences are fully accounted for in the detailed discussions of the subject in previous reports of this series. For figures of any one year an excess of mining over smelting and refining is indicated by larger returns in the mines

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