Communications respecting Hocks of Scandinavia. 299 



the immediate neighbourhood of crystalline mountains seems 

 to have lost all stratification ; but which, on the other hand, 

 frequently presents a cleavage parallel with the surface of the 

 contiguous gneiss. It is this very same phenomenon which 

 one so often meets with in our Alps, and which may increase 

 the difficulty of the answer to the question, whether the 

 slate character of the crystalline rock corresponds to a for- 

 mer state of stratiiication ? I have a very lively recollection 

 of that excursion across the glacier of the Grindelwald, which 

 I had the pleasure of making in yoiir company. We saw 

 that the limestone on the front of the Mettenberg exhibited 

 a distinct and almost horizontal stratification. We then ob- 

 served how gradually towards the posterior part, along the 

 glacier, the sti-atification disappeared ; and in place of it on 

 the south side of the mountain, where the glacier of the 

 Grindelwald joins the Mer de Glace, and the gneiss appears, 

 a nearly perpendicular and very distinct separation in tlie 

 limestone, running parallel with the surface of the gneiss, 

 becomes apparent. This proves, however, that at the change 

 of these formations, the cflFect of the rock-metamorphoses had 

 extended, although in a slight degree, to the surrounding- 

 parts ; and, on the other hand, that the separation of strata 

 in limestone is a phenomenon which is first and most easily 

 lost by external agency. 



In the alum-slate of the neighbourhood of Christiania there 

 is to be found beds of greenstone and eurite, which appear 

 as veins wherever the stratification of the alum-slate is in- 

 tersected by tabular masses of greenstone. I lately men- 

 tioned to you in a former letter, that among the transition 

 rocks in the Hartz mountains also, greenstone appears to 

 occur more frequently in beds than in the shape of veins. If 

 in a mountainous region, we suppose alternate layers of dif- 

 ferent characters, of which the one kind are more suscepti- 

 ble of metamorphoses than the other, then we shall see tlie 

 former assume the crystalline structure, while the latter re- 

 tain their original character : thus we shall have the appear- 

 ance of beds of crystalline formation in the midst of un- 

 changed rock. But such changes of a rock in the midst of 

 others that remain unchanged, is, of course, to be accounted 

 for by no external agency, occasioncil by volcanic rocks, for 



