THE IRON-ORE SUPPLIES OF 

 THE WORLD 



By J. W. GREGORY, D.Sc, F.R.S. 



Professor of Geology at the University, Glasgow 



Iron may be said to be the material in which modern civilisa- 

 tion chiefly finds its expression. Substitutes could be found 

 for any other of the metals in use or the world could go on 

 without it ; even if our coal supply failed other sources of 

 heat and power would still be available : but modern civilisa- 

 tion would inevitably wither in a serious iron famine, as cheap 

 iron is required for the construction of the appliances used in 

 the cultivation and preparation of our chief foods and in the 

 manufacture of our clothing ; it is also indispensable as a 

 building material in our modern cities and in providing the 

 means of rapid transport which render their existence possible. 

 The exhaustion of the world's supply of iron ores has been 

 repeatedly predicted and one essential difference between 

 the mode in which ores of iron and those of most other 

 metals occur seems at first to give some plausibility to 

 such forecasts. The lodes of gold, copper and tin met 

 with at or near the surface of the earth continue to great 

 depths beneath it. Thus gold is being worked in Bendigo at 

 a depth of 4,700 feet, copper in the Lake Superior region 

 at over 5,000 feet and tin in Cornwall at 3,000 feet ; no 

 doubt such ores occur at even far greater depths. The best 

 ores of iron, on the other hand, occur only at comparatively 

 shallow depth : instead of being derived from solutions rising 

 from the deep interior of the earth, they have been deposited 

 on the surface or by water percolating downward from the 

 surface ; on this account, oxide ores in sufficient bulk and 

 purity to be of present commercial importance are practically 

 confined to the layer accessible to water containing oxygen ; 

 as that depth is limited, it appears most probable that the high- 

 grade ores of iron will not continue downward to depths below 

 the earth's surface in any way comparable with those reached 

 by mines of copper, gold and tin. 



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