PRESIDENTIAL ADDRESS, 501 
limited depths to which water can carry down these gases. On the theory, 
however, that these ores are primary segregations from deep-seated igneous rocks 
there need be no limit to their depth. They would rather tend to increase in size 
downward, while maintaining, or even improving, in the richness of their metallic 
contents. For these bodies may be regarded as fragments of the metallic bary- 
sphere which have broken away from it and revolve around it like satellites 
floating in the rocky crust. On this conception these ore bodies would be of as 
great interest to the student of the earth’s structure, as their existence would be 
reassuring to the ironmaster, haunted as he is by constant predictions of an iron 
famine at no distant date. It is no doubt true that many of the richest, most 
accessible, most cheaply mined, and most easily smelted iron ores have been ex- 
hausted. The black-band ironstone and the clay iron ores of the coalfields, which 
gave the British iron industry its early supremacy, now yield but a small propor- 
tion of the ores smelted in our furnaces. ‘lhe Mesozoic beds of the English Mid- 
lands and of Yorkshire still supply large quantities of ore. Nevertheless the 
British iron industry is becoming increasingly dependent on foreign ores, So it 
would be pleasant to find that the Scandinavian iron mines are not subject to the 
usual limits in depth. I fear the typical iron deposits of Middle Sweden and of 
Gellivara will follow the general rule; but Kiruna may be an exception, and its 
ores may continue far downward along the surface of its sheet of porphyrite. 
The uncertainty in this case lies in the extent of the subsequent enrichment and 
enlargement of the bed; if most of the ore is due to secondary deposition, then it 
may be restricted to the comparatively shallow depths at which this process can 
act; and though that limit will be of no practical effect for a century or more to 
come, the ore deposit may be shallow as compared with some gold-quartz lodes. 
The geological evidence may convince us that all the economically important iron 
ores are limited to shallower depths than some lodes of gold, copper, and tin; but 
this conclusion shall not enroll me among the pessimists as to the future of the iron 
supply. ‘Twenty years ago a paper on the gold supplies of the world was read to 
the Association at the request of the Section of Economics. About the time that 
the report was issued, there were sixty-eight mining companies with a nominal 
capital of 73,000,000/. at work upon the Rand. Nevertheless, the author, accepting 
the view that ‘the future of South African gold-mining depends upon quartz 
veins,’ concluded: ‘ There is as yet no evidence that the yield will be sufficient in 
amount to materially influence the world’s production. As regards India, the 
prospect is still less hopeful.’ 
That quotation may be excused, as it is not only a warning of the danger of 
negative predictions, but of the unfortunate consequences that happen when geo- 
logists are unduly influenced in geological questions by the opinions of those who 
are not geologists. In economic Geology, as in theoretical Geology, we should 
have greater confidence in the value of geological evidence. Negative predictions 
are especially rash in regard to iron, it being the most abundant and widely dis- 
tributed of all the metals. The geologist who knows the amount of iron in most 
basic rocks finds it difficult to realise the possibility of an iron famine; he can 
hardly picture to himself some future ironmaster complaining of “iron, iron every- 
where, and not a ton to smelt.’ There are reserves of low grade and refractory 
materials which the fastidious ironmaster cannot now use, since competition 
restricts him to ores of exceptional richness and purity. When the latter fail, an 
unlimited quantity could be made available by concentration processes. The vast 
quantities of iron ores suitable for present methods of smelting in Australia, 
Africa, and India show that the practical question is that of supplies to existing 
iron-working localities, and not of the universal failure of iron ores. 
VI. Mining Geology and Education. 
The genesis of oresand the extent of future ore supplies are intimately con- 
nected questions, and the recognition of this fact has led to the remarkable growth 
of interest in economic Geology. This wider appreciation of the practical value of 
