dividends of all the mines and associated metallurgical works of the United States on the basis of 30 years. Each and every one of the mines producing at any given time will not continue to do so for 30 years. Relatively few of them will do so. However, the places of those that fail and drop out will be taken by new mines developed in properties for which no present value is inventoried. Experience has amply proved that this is a safe assumption, for the production of coal, iron, and the other metals and minerals by the mines of the United States in the aggregate has steadily increased, year by year.
It remains then to determine the amount of the annual net earnings of all the mines. This is a difficult and more or less conjectural subject, for many of the most important mines are owned by industrial corporations that do not report mine dividends separately. For example, this is the case with the very large and very important iron mines owned by the United States Steel Corporation. We must resort, therefore, to indirect methods.
The net income of the mines of the United States in 1916 as reported by the Bureau of Internal Revenue was about $800,000,000. In that year the dividends paid by 127 copper, lead and zinc and precious metal mines listed by the Engineering and Mining Journal amounted to $170,388,378. Consequently the total net income of the mines of the country was 4.7 times the amount of these reported dividends. Allowing for some underestimation in the reported net income, especially for the omission of that of metallurgical works, we may assume roughly that the total net carnings of the industry amounted to about five times
