Address to Section C, Geology. 457 
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 barysphere 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 exhausted. 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 proportion of the ores smelted in our furnaces. The Mesozoic 
beds of the English Midlands 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 gold-mines. 
The geological evidence may convince us that all the economically 
important iron ores are limited to shallower depths than lodes of gold, 
copper, and tin; but this conclusion shall not enrol 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. Never- 
theless, the author, accepting the view that ‘‘the future of South 
African gold-mining depends upon quartz yeins,’’ 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 geologists 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 distributed 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 everywhere, and not 
