14 
ERUPTIVE ROCKS AND METAMORPHOSED SILURIAN, &C. 
give to the sedimentary masses a peculiar and subcrystalline character. Of such 
eruptive rocks contemporaneous with the Silurian and older palaeozoic strata, we 
shall, however, hereafter treat in describing the Ural Mountains. Here we simply 
note their absence, as accounting, in some measure, for the small vertical dimen- 
sions of the Silurian formations of Norway which have evidently been accumulated 
in a sea that has been exempted from those contemporary igneous evolutions, which 
in many other tracts, have naturally tended to swell the thickness of the ancient 
formations. 
The mineral changes however produced by the eruptive rocks upon the Silurian 
beds of Norway are, indeed, as beautiful and striking as in any region that we ever 
examined. Thus in the tracts north-west of the Steens fiord and in the Solvsherg, 
where igneous rocks protrude, it may be said, that the black shales (Lower Silu- 
rian) are changed into hard subcrystalline schists (the Harte Scliiefer of Keilhau, 
or Kiesel Schiefer of the Germans) ; but however altered, the original character 
of the stratum is discernible, and fossils are found in it at intervals. On the left 
bank of the Drammen, opposite Vigersund, a lower fucoid sandstone in contact 
with greenstone becomes a quartz rock. At the town of Drammen, eruptive 
rocks of granite and greenstone, apparently passing into each other, exhibit in the 
adjacent escarpments fragments of highly altered micaceous red sandstone (Old 
Red) and Lydian stone, surmounted by and included among amygdaloids. At 
Djelebeck or Jelebeck, to the north of Drammen, granite forming the hill called 
Paradis-backen, throws off the Pentamerus limestone, which though metamorphosed 
into a saccharoid marble and charged with garnets in the neighbourhood of the 
granite, becomes less and less altered as it recedes from that rock, and then con- 
tains its usual fossils 1 . 
Following the same bands of younger granitic and porphyritic rocks to the 
south, they are seen to spread out and occupy nearly the whole of the southern 
portion of the palaeozoic basin, crowning considerable heights, and extending into 
the promontories on either side of Laurvig and Fredricksvarn. There they form 
1 We examined this altered rock with our friend Professor Forchhammer, who thus writes of it : — “ This 
impure limestone contains, besides carbonate of lime, some carbonate of magnesia, alumina, oxide of iron 
and silica. The compact carbonate of lime has assumed a granular form and has become white marble ; 
the magnesia has lost its carbonic acid, and has combined with lime and silica to form the mineral tremo- 
lite ; and the oxide of iron has combined with alumina, lime and silica, to form greenish and beautifully 
crystallized garnets.” — Trans. Brit. Assoc, for 1844, p. 165. 
