M. Keilhau's Theory of Granite and other Rocks. 27 J 



rock was near enough to cause the occurrence of alum-slate ; 

 and the latter is never found passing into hard slate, although 

 quite near the granite. But there we find chiastolite, a re- 

 markable proof that the strong tendency to crystallization 

 nevertheless existed also at those places. We remarked of 

 eurite-porphyry, which, for reasons now clear, occurs chiefly in 

 alum-slate, that it has not the power of producing any altera- 

 tion on that rock at the junction; thus affording a sign of a 

 power acting against these metamorphoses, whether that power 

 be in the condition of the alum-slate itself, or in the causes of 

 the formation of the alum-slate (contact with the primary se- 

 ries). 



That otherwise, the porphyries in general do not produce 

 these remarkable contact phenomena at the granite or at the 

 primary boundaries, is a fact which deserves to be again men- 

 tioned. Melted masses, whether they afterwards become har- 

 dened into a porphyry or a granite, must, by their heat, have 

 produced nearly the same actions. But if we assume that these 

 formations of minerals, and changes at junctions are results of 

 actions that required much more special conditions, we are no 

 longer surprised to see them sometimes only weak, and at 

 others entirely awanting in masses, where, according to the 

 volcanic interpretation, they ought to have been developed in 

 the highest degree. 



But, for the present, we must be satisfied with giving the 

 above details. Whoever, in reference to our very remarkable 

 transition district, may wish to test more exactly the views now 

 given, by means of a larger collection of facts than I have here 

 noticed, will find sufficient data regarding highly instructive 

 localities in the work to which I have more than once referred. 



Before proceeding, in the next place, to pass on to the con- 

 sideration of the massive formations of other countries, which 

 ought to be placed alongside of those occurring with the fos- 

 siliferous transition series of Norway, I would add, from my 

 still unpublished work, one general reflection in regard to the 

 chief idea in the proposed theory, — the idea, namely, that crys- 

 tals, and even whole aggregates of these chemically and mor- 

 phologically most perfectly formed inorganic natural bodies, 

 can proceed from an indeterminately compound, formless, nia- 



t2 



