M. Keilhau"'s Theory of Granite, and other Rocks, 81 



rocks in such districts are the products of eruptions, still it 

 cannot easily be admitted that such enormous outpourings of 

 two such entirely different materials should have taken place 

 at one and the same time at points lying so near to each other. 

 A priority must undoubtedly be assigned to the appearance at 

 the surface of the one or the other. But in doing so, so far as 

 I can see, we cut off* the only possible approach to assigning, 

 according to the eruption theory, a kind of cause for the transi- 

 tions, viz. that the porphyry and granite on meeting at one time 

 in a fluid state, became blended together at the points where 

 they encountered each other. 



But what may be still more unwelcome than the phenomena 

 of the boundaries of granite and porphyry, to certain theorists, 

 is, that we observe transitions from the massive to the stratified 

 rocks. One of the greatest errors in modern geology, is the 

 distinct separation, proceeding Jrom the genetic mode of viewing 

 the subject, between stratified, or what are termed normal foN 

 mations, and abnormal formations. In the manner in which 

 it is wished that this separation should be understood, it is ih 

 fact altogether contrary to nature ; for, according to this sys- 

 tem, there cannot and must not be any real transition thought 

 of from the type of one of the two great classes to that of the 

 other ; and yet such a transition exists in thousands and thou- 

 sands of places. This deviation from truth is its own punish- 

 ment. Thus, we see some geologists who are under the neces* 

 sity of denying a fact so clear as the transition of granite into 

 gneiss ; while we find others who rank gneiss, mica-slate, and 

 I know not how many other stratified rocks, in the class of 

 massive formations. 



Let us examine the suite of specimens of mountain-rocks 

 from one of the most instructive localities in our territory, that 

 of Solvsberg* in Hadeland. In the first piece, we recognise 

 the usual siliceous slaty rock into which clay-slate and calca* 

 reous clay-slate pass when near the granite boundary, a rock 

 which exhibits distinct petrifactions, and in which, likewise, stra- 



• The remarkable locality of Solvsberg, mentioned in the text, is situated 

 near the Rands-Fiord, and but a little to the west of the great road froift 

 Christiania to Bergen and Trondhjeni. — Edit. 



VOL. XXV. NO. XLIX. JULY 1838. P 



