378 SCIENCE PROGRESS 



Material that in one place or time may be quite valueless 

 may become a useful ore through some change in political or 

 commercial conditions. For example, there are said to be large 

 supplies of high-grade ore available in Honduras but it has 

 not yet been worth any one's while to test these reports : 

 no doubt, if Honduras were a great importing country the ore 

 would be investigated at once, as it could then be exported 

 owing to the cheapness of return freights. The working of 

 British ores, on the other hand, is retarded because the ships 

 that export our coal bring back ore at an abnormally low rate. 



The conditions controlling the development of an iron ore 

 are so complex that no simple rules can be stated and so some 

 of the reports include ores containing as little as 20 per cent, 

 of iron; others restrict the limit to a minimum of 30 or 40 

 per cent, or even 60 per cent. The lower-grade ores can be 

 used if they form a good smelting mixture with richer ores 

 or after the others are exhausted. Twenty years ago the 

 ores used in the United States contained an average of 62I per 

 cent, of iron ; at the present time cargoes containing over 60 

 per cent, are exceptional, the average being about 50 per cent. ; 

 even cargoes of 40 per cent, iron are used and in Alabama ores 

 are mined and included in the reserves having on an average as 

 little as 36 per cent, of iron. 



Though the data collected by Dr. Sjogren show that the fear 

 of an iron famine is idle, the supply of ores containing 60 per 

 cent, of iron is acknowledged to be comparatively limited. The 

 total supplies of such ore are estimated at 1,300 million tons 

 of known ore and some 68y million tons of potential reserves. 

 Of the known supplies, about 1,100 million tons or more than 

 four-fifth of the total known amounts are in Sweden. In America, 

 excluding ores too rich in titanium to be of present value, the 

 reserves amount to only 58 million tons and are limited to 

 Mexico and the West Indies ; Australia reports 49 million tons 

 in Westralia and Tasmania and an additional 34 million tons of 

 potential reserves in South Australia and Queensland. In Asia 

 there are 530 million tons, all belonging, however, only to the 

 potential reserves. 



At the present time about 60 million tons of pig-iron are 

 produced every year ; the production has on the whole more 

 than doubled in every twenty years, so that if we were depen- 

 dent on ores containing 60 per cent, or more of iron, the known 



