PRESIDENTIAL ADDRESS. 499 
Dickson (1903), He has shown that the sulphides are separated from the barren 
rock by sharp boundaries, and without any indication of a passage between them ; 
that the fragments of ore in the rock have short corners, whereas, had they grown 
in a molten magma, the angles would have been rounded, and the faces corroded. 
Most of the ore, moreover, occurs as a cement filling interspaces between broken 
fragments of barren rock and along planes of shearing, The Sudbury ores, there- 
fore, appear to have been deposited from solution during or after the brecciation of 
the rocks in which they occur, and long after|their first consolidation. If Dickson's 
facts be right, the Sudbury ores are necessarily aqueous and not igneous in origin, 
3. Scandinavian Iron Ores.—The other important mining field of which the 
ores are claimed as of igneous origin is Swedish Lapland. Its ores are rich and 
the ore bodies colossal. One mine, Kirunavaara, yielded over one and a half 
million tons of ore in 1906, and according to a recent agreement with the Swedish 
Government the annual output of ore from that mine may be raised to three million 
tons by 1913. 
The chief mining fields of Lapland, although situated to the north of the Arc‘ic 
Circle, have long been known; for some of them contain veins of copper which 
were worked, for example, at Svappavaara in the seventeenth century. The iron 
ores, however, could not be used until a railway had been laid through the swamps 
of Lapland to carry the ores cheaply to the coast. In 1862 an ill-fated English 
company began a railway to the Gellivara mines, and thirty years later this was 
completed across Scandinavia, from the head of the Gulf of Bothnia at Lulea to 
an ice-free port at Narvik, on the Norwegian coast, 
This railway, the most northern in the world, passes the two great mining 
fields of Gellivara and Kiruna. The mining field of Kiruna is the larger and at 
present of the greater geological interest, as its structure is simpler and its rocks 
less altered. 
The ore body at Kiruna outcrops along the crest of a ridge two miles long, and 
it is continued beneath Lake Luossajarvi to the smaller but still immense ore body 
of Luossavaara. At Kiruna the ore rises to the height of 816 feet above the sur- 
face of the lake, and it varies in thickness from 30 to 500 feet, with an average 
thickness of about 280 feet. According to the report by Professor Walfrid 
Petersson,’ submitted this year to the Swedish Parliament, Kirunavaara contains 
200 million tons of ore above lake-level, and Luossavaara another 224 million tons. 
The ore is high-grade. According to Lundbohm 60 per cent. of the trial pits 
showed a yield varying from 67 to 71 per cent. of iron, and 21 per cent. of them 
showed a yield of from 60 to 67 per cent. of iron. The average of nineteen 
analyses published in Professor Petersson’s recent report gives the contents of iron 
as 64:15 per cent. Unlike the Taberg and Routivaara ores, the percentage of 
titanium is very low; thus in nineteen analyses given by Petersson the average of 
titanic acid is only 0:23 per cent., and it varies in the specimens from 0-04 to 
0'8 per cent. 
The ore lies between two series of acid rocks, which hare been very differently 
interpreted, but will no doubt be fully explained by the researches now in progress 
under the direction of Mr, Lundbohm. The rocks were first called halleflinta, 
as by Fredholm, and regarded as of sedimentary origin. They are now accepted 
as an igneous series, associated with some conglomerates, slates, and quar'zites. 
The ore body itself is bounded on both sides by porphyrites, of which that on the 
lower or western side is more basic than that overlying the ore to the east. The 
basic western porphyrite is in contact with a soda-augite syenite of which the 
relations are still uncertain. Interbedded with the overlying eastern porphyrite 
are rocks that appear to be volcanic tuffs, and both in the tuffs and in the upper 
porphyrite are fragments of the Kiruna ore. 
Three main theories of the genesis of the Kiruna ores have been proposed. 
Their sedimentary origin was urged on the ground that they occur regularly 
interstratified in a series of altered sediments, and that the ores, therefore, are also 
sedimentary. This view may be promptly dismissed, since the adjacent rocks are 
igneous. 
1 Bihang till Rikd. Prot., 1907, 1 Saml., 1 Afd., 84 Haft, No. 107, pp. 213, 217, 
K K 2 
