300 Communications respecting Hocks of Scandinavia. 



this M'ould have produced like metamorphoses in all the 

 rocks, instead of leaving the fossiliferous slates, in wliich 

 those metamorphic rocks lie, in their original condition. 

 Thus, Nature here gives us a hint that the cause of these 

 metamorphoses could not have been produced by external 

 agency. But tliis does not exclude the existence of the vein- 

 genous appearance of crystalline rocks, which also occur in 

 Norway. Certainly a state of softness has frequently arisen 

 during those changes, especially in all those which have pro- 

 duced the granular crystalline rocks. Were there now such 

 a mass in the act of metamorphoses, under great pressure, 

 we should see the mass penetrating through fissures into the 

 superincumbent and subjacent rock, and thus we should have 

 veins running upwards as well as downwards. In Norway we 

 meet with some of the latter kind, as for instance the rhombic 

 porphyry, which, issuing from the mass of porphyry lying above 

 the sandstone, ramify into the subjacent transition rock. 



Greenstone and eurite * are consequently very abundant in 

 the ti-ansition rock district of Christiania. A very peculiar 

 appearance occurs about half a Norway mile north of the 

 town. Here, in a dark-green mass of rock, appear angular 

 fragments of granite, and various kinds of gneiss and horn- 

 blende, intermingled without the slightest ordei\ I have 

 brought specimens, in which we see all these varieties of rock 

 together. I confess that I doubted the possibility of an ex- 

 planation. The Yulcanists, however, are at once ready with 

 one. They say, the greenstone has, during its upward pres- 

 sure, torn off fragments from the mountain whilst piercing 

 through it ; and they make these different kinds of rock meet 

 together in the unexplored lower regions, and there produce 

 the formation. When I examined the rock more closely, it 

 appeared to me as if the heterogeneous enclosures, instead of 

 being parts of a breccia, were rather the remains of a con- 

 glomerate, which had become partly affected by the green- 

 stone, so that only isolated hard grains which resisted the 

 influence were left behind, and are now, of course, deprived 

 of their former rounded form. I anticipate much pleasure 



* Eurite is a very fine, granular, nearly compact, granitic mixture, with pre- 

 dominating felspar. With imbedded small crystals of felspar it forms euiite- 

 porphry. 



