OUTLOOK FOR IRON KEMP. 



content with the general significance of the results, 

 they supply us with trustworthy values. 



295 

 On the whole, 



Range. 



No. of 

 analyses. 



Maximum. 



Minimum. 



Average. 



Marquette . 

 Menominee 



Gogebic 



Vermilion. . 



69.77 

 65.20 

 65.45 

 67.54 



53.02 

 52.18 

 54.95 

 60.20 



62.33 

 60.00 

 62.09 

 64.50 



These figures represent the good old times when specular ore was 

 almost the only one produced and before the soft ores began to be a 

 serious factor. They are, however, significant, in that customary 

 working percentages, such as these, very probably were not without 

 their influence in the estimates of the life of the ranges, as set forth 

 by several of the writers whose opinions were cited in the introduc- 

 tion to this address. 



Eaphael Pumpelly, in connection with the summaries of the Tenth 

 Census,^ estimated on the best and most comprehensive data which 

 we have ever had, the general average of iron ores for the United 

 States at 51.22 per cent iron. The maximum average percentage 

 among the States was that of Missouri, 60.01 (but Michigan had 

 59.57). The minimum was West Virginia, 37.92. Pennsylvania, the 

 largest producer of ore in that year, gave 45.28. On the basis of ore , 

 production and pig-iron production, allowance being made for mill 

 cinder, foreign ores, etc., John Birkmbine estimated for the Eleventh 

 Census ^ an average of 51.27 for the country at large. An appreci- 

 able error crept in, however, in assuming pig iron to be entirely iron, 

 whereas it is only about 95 per cent or less metallic iron. We can 

 hardly compare this figure with the one given by Prof. Pumpelly 

 which was based on actual analyses of samples. If we credit the 

 7,000,000 tons of pig iron, as used by Mr. Birkinbine, with 95 per 

 cent iron, the average is -18.71, which indicates an appreciable falling 

 off in yield in 10 years. 



General estimates of average percentages which will be trust- 

 worthy are difficult to carry out on the basis of annual statistics of 

 tons of ore and tons of pig iron. Foreign ores contribute to an 

 appreciable degree, and their yield can only be estimated. Stocks 

 of mined ore, stored at furnaces or mines at the end of a year, are 

 naturally credited to that year, but they are not turned into pig 

 iron until the following twelvemonth. Mill cinder is also a con- 

 tributor of iron to the extent of a small percentage of the total. 

 The data for all these corrections are not available for a long period 

 of years, and, therefore, all could not be introduced in the following 



1 Tenth Census, vol. 15, 19, for the year 1879. 

 * Volume on Mineral Industries, p. 10. 



