258 Naumann on Primitive Formations, 



inferior energy may have been compensated for by their long 

 duration. But while these philosophers do not express a decided 

 opinion regarding the real character of these transforming pro- 

 cesses, G. Bischof and Haidinger are inclined to suppose that a 

 long continued percolation of water through the rocks* has pro- 

 duced a substantial alteration and recrystallization, in the same 

 way as must have taken place in the production of certain altera- 

 tion pseudomorphs.f Many believe it possible to indicate more 

 nearly the sedimentary rocks from which these cryptogenous rocks 

 have been produced. Thus, in 1833, Hitchcock was of opinion 

 that the gneiss had probably been previously a coarse micaceous 

 sandstone, a view which Durocher also adopted, while Forch- 

 hammer believed it possible to prove that the gneiss of Egeberg, 

 near Christiana, was produced from the alum-schist, which occurs 

 there. I 



We have already remarked however that parallel structure and 

 stratification, cannot in every case, be considered as decisive proofs 

 of sedimentary origin. Even MaccuUoch, in other respects a 

 zealous supporter of the metamorphic theory, admits this. He 

 says expressly that he is obliged to explain the parallelism of the 

 laminae of mica, so often adduced, as a proof of the sedimentary 

 deposition of gneiss, in quite another manner, because even hy- 

 persthenite sometimes shows a parallel deposition of its crystals 

 of hypersthene, and at Kerrera a trap which occurs in veins is, like 

 mica slate, filled with scales of mica, all lying parallel with the 

 aides of the vein. 



We have also already mentioned the doubts brought forward by 

 Hofi'man and Riviere against the view that widely extended gneiss 

 areas are to be considered as altered sedimentary masses. De 



* So early as the year 1785, Von Trebra enunciated the view that the 

 alteration of whole mountain masses, for example, of granite into gneiss, 

 and of greywacke into clay slate, had been caused by a very long con- 

 tinued process of alteration, which he characterised as a sort of fermen- 

 tation, and which was produced essentially by the circulation of water, 

 and by the action of heat. Since these causes, which although unper- 

 ceived, are nevertheless thoroughly active, and still at work, and will 

 continue, so as long as circulation goes on in the immeasurable round 

 of nature, he is convinced that the alterations, decompositions and re- 

 compositions which they produce everywhere in the interior of the rocks 

 will continue as long as the world itself.— (Erfahrungen von Innern der 

 Gebirge, p. 48.) 

 t Lehrbuch der Phys. und Chem. Geologic, II. 247. 

 t Journal fiir Praktische Chemie. Bd. 36, 1845, S. 404. 



