350 Prof. Keilhau on the Formation of 



opinions I have now offered on the mode of investigation 

 at present pursued in geology ; and at the same time, to jus- 

 tify the method which has been adopted by myself, and which 

 has been so strongly blamed. With this view, I intend to 

 treat, first, of crystalline granular limestone, or, to make use 

 of a shorter expression, of marble ; next, of several of those 

 peculiar mineral masses, which are most easily designated by 

 the name of " contact-formations ;'' and, lastly, to say some- 

 thing on the crystalline silicide-slates, and the unstratified 

 crystalline silicide-rocks. I should very willingly have em- 

 braced this opportunity of taking also into consideration the 

 history of gypsum and dolomite, but the fear of being thought 

 much too digressive, causes me to refrain. The subject of the 

 crystalline silicide-rocks is, on the other hand, suitable for an 

 additional reason, viz., that these constitute the most import- 

 ant component parts of the country, to whose description I am 

 about to offer contributions ;* and I may remark, that marble 

 also is an essential member of the geological formations of 

 Norway. 



Crystalline Limestone or Marble. 



The various modes of occurrence of crystalline limestone in 

 groups of fossiliferous rocks, are the most instructive. It some- 

 times also itself contains organic remains. Not unfrequently 

 it presents itself in these groups in the four following ways: — 

 1. As larger or smaller spheroidal or kidney-shaped masses, ly- 

 ing included in strata, whose sedimentary origin cannot be 

 denied. 2. In the form of entire strata, interposed between 

 equally distinctly sedimentary beds, and situated quite in the 

 midst of their undisturbed order of succession. 3. As a mid- 

 dle portion of such strata, and gradually passing on both sides 

 into uncrystalline limestone. 4. As a terminal portion of strata, 

 which are elsewhere composed of uncrystalline limestone, and 

 which, at their crystalline termination, are in contact with 

 some rock entirely different from the limestone. 



• * Professor Keilhau here alludes to a geognostical description of Norway, which 

 he is preparing for publication, and which we feel assured will prove a very valu- 

 able contribution to Geological Literature.— Edit. 



