304 REPORTS ON THE STATE OF SCIENCE. 
rocks, as well as from the fact that they frequently present all degrees of 
transition into the normal rock. 
The ore deposits belonging to this class are not confined to any of the 
ore provinces mentioned above, but occur scattered all over the peninsula, 
both in Sweden and Norway. 
4. Ores associated with the Metamorphosed Schists of Cambro-Silurian 
Age chiefly occur in the mica-schists group characterised by mighty beds 
of limestone. 
The deposits of this class are geologically characterised by belonging 
to a ferriferous formation of vast horizontal extent, occupying nearly the 
same geological horizon, and they occur as regular members of this sedi- 
mentary scries. If the ores are to be considered as primary sedimentary 
deposits, or if they constitute secondary concentrations of leaner iron- 
bearing formations, is still an open question, not only of theoretical but 
also of great practical importance. 
On the whole, one may consider these deposits as the roots or the 
deepest comparatively unconcentrated parts of regionally metamorphosed 
chemical deposits laid open by the deeply penetrating firths and valleys 
of the Norwegian coast, the upper probably more concentrated and thus 
richer parts of the same deposits having been destroyed by erosion. 
These ores, which form a geologically very well-defined class, are also 
territorially confined to a certain ore province, that of Northern Norway. 
5. Contact Formations connected with Acid Eruptive Rocks of post- 
Silurian Age occur in the Archean gneisses and in the Silurian limestones 
and argillaceous schists of the Christiania Silurian basin. 
The igneous rocks of the Christiania region comprise, according to 
Brégger, several different types, of which the more basic, 7.e., gabbro- 
diabases, basic pyroxene-mica, and nepheline-syenites and quartz-bearing 
pyroxene-syenite, are the older, and the acid types, 7.e., red quartz-syenite 
(Nordmarkite), soda granite (Grorudite) and granitite are the younger. 
The intrusives are bordered partly by Archean rocks, partly also by 
the Silurian strata, and by porphyry outflows. The contact deposits are 
found in all these different pregranitic rocks. Most of the deposits are 
connected with the red quartz syenite (Nordmarkite), some of them with 
the soda granite (Grorudite) and with the granitite. 
These ore deposits are, though many in numbers, yet quantitatively 
too insignificant to play any commercial réle. In earlier times several 
hundreds of them were worked. 
6. Lake and Bog Ores belonging to the most recent Geological Period.— 
These ores occur scattered over most provinces of Sweden and the southern 
part of Norway ; yet they occur amply only in such regions of the country 
where the ground consists of moraines and gravel, and they are found 
more sparingly in the parts of the country which are covered by glacial 
and post-glacial marine deposits. In short, the lake and bog ores are 
most frequent above the marine level of the Glacial period. A certain 
connection with the distribution of the peat-mosses is indicated. 
The different geological ore groups defined above are characterised by 
mineralogical and chemical properties, which have determined their 
technical utilisation. 
The lake and bog ores of Group 6 formed, on account of their cheap 
exploitation and easy reduction, the raw material of the oldest iron manu- 
facture in the Scandinavian countries, 1nd were used long before the 
blast-furnace process was known. Carl von Linneus for this reason called 
