6 P. A. øyen. 



The hornfels is a characteristic rock of very great 

 importance to fix the line of transportation, as different 

 colours may trace different places of derivation. As a rule, 

 we find them to be grey, tinged with red, green, blue and 

 yellow, but we also find them to be sometimes quite black- 

 coloured, contact-metamorphosed schists. To the very same 

 group may also be referred a rather rare occurrence of con- 

 tact-metamorphosed rhomben-porphyry, such as we find this 

 rock to be in some places preserved as shoals left on the 

 upper surface of nordmarkite-laccolites in the region of the 

 Lake of Alunsjøen to the north-east of Christiania. The 

 typical hornfels was represented by eleven specimens, and the 

 rhomben-porphyry by three specimens, altogether a number of 

 fourteen individual stones of contact-metamorphosed rocks. 



It is highly interesting to see that the laccolite-rocks 

 to the north of Christiania constitute no less than about 

 three fifths out of the whole number of blocks and stones 

 of the gravel. Practically it will make no difference for 

 our present purpose, whether the blocks and stones belong 

 to the typical, reddish-coloured nordmarkite or not. I, there- 

 fore, have put in one and the same group, as well this well- 

 known rock as the grey akerite. And, in spite of having 

 especially numbered fifteen specimens of the porphyric syenite, 

 such as we find the marginal faciès of nordmarkite to be 

 developed in several places, for instance in the neighbour- 

 hood of Stenbrovand to the north-east of Christiania, and 

 in spite of having likewise numbered fifty specimens of 

 syenite-porphyry, either this rock belongs to the marginal 

 faciès of nordmarkite or to the adjoining dykes, I find just 

 as little reason for separating those rocks of the two last- 

 named types from the rocks of the central type above men- 

 tioned. Summing up the specimens of porphyric syenite and 



