296 



ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1916. 



estimates. The importations could, however, be deducted, and to 

 them an average of 58 per cent iron has been arbitrarily assigned. 

 The results obtained are so variable that their significance is rather 

 one of degree than of actual individual accuracy. The statistics are 

 chiefly taken from the Mineral Resources for 1910, page 76. Long 

 tons are used. 



1 These totals are the apparent iron ore consumptions as given in the Mineral Resources, United States 

 Geological Sm-vey, for 1912, p. 162. They diller from the totals of production in the previous tables 

 because corrected for unsmelted stocks, exports, and zinc residuum. No correction is made for mill 

 cinder. 



The variations shown above are so pronounced as to cast some 

 doubt upon the accuracy of the individual percentages, but we may 

 have some confidence in the general tendencies shown. We can not 

 but be impressed Avith the apparent practice of the mining companies 

 of using lower grade ore in good times, as shown by high produc- 

 tion, and saving higher-grade ores for bad years. So far as recent 

 years are concerned, we can only say that the general grade has de- 

 clined, although it does not appear to be as low as it was in 1870, 

 when the brown ores of the East Avere so large a factor in produc- 

 tion. It must be to-day well below 50 per cent. 



In the last column, and for the years beginning with 1890, are 

 given calculations of average yield, prepared by E. C. Eckel in his 

 valuable manual on " Iron Ores," published in 1914. The same 

 figures for apparent iron ore consumption have been used as in the 

 calculations given in the first column of the present table; that is, 

 the total annual production has been increased by imports and by 

 zinc residuum (i. e., used for spiegeleisen by the New Jersey Zinc 

 Co.), and diminished by exports and by stocjis on hand at the close 

 of the year. The zinc residuum is only 0,2 to 0,4 per cent of the 

 total and makes little difference. But a decided difference arises in 

 calculating the yield of American ores if one assumes that pig iron 

 is pure iron, and lets the much richer importations of foreign ores 

 enter into the calculation. These last two elements in the problem 

 explain the wide divergence in percentages of from 4 to nearly 8 

 per cent between the average values given in this paper and those 



