^90 M. Keilhau's Theory of Granite and other RocTcs. 



granitoidal amphibolite, and aphanite ; also red and black por- 

 phyries of many varieties ; basaltic rocks and amygdaloid, to- 

 gether with porphyry-conglomerate. In the Upland territory, 

 which, in comparison with that of Christiania, is extremely de- 

 ficient in these kinds of mountain-rocks, porphyry chiefly oc- 

 curs, and also somewhat smaller portions of granite and green- 

 stone. 



Granite and Syenite. — Granite and syenite exhibit precisely 

 similar relations, and frequently pass into each other. Tliey 

 are to be regarded as but one formation. In the Christiania 

 territory they appear at the surface in tracts, which, taken toge- 

 ther, amount to more than a third part of the whole area of that 

 portion of country, and two of the districts which they form 

 have each a superficies of upwards of 200 square English miles ; 

 with respect to which it is to be remarked, that the form of 

 these districls is generally not particularly stretched out longi- 

 tudinally, so that we could not, for instance, compare them with 

 the Cleveland dyke in England, which also occupies an extra- 

 ordinary extent, but only in one direction. Neither could we 

 think of comparing these large expanses of granitic masses 

 with those great horizontal sheets of trap, wbich, we are told, 

 in Iceland, for example, present a still larger surface. As to 

 the manner in which these masses join with the stratified rocks, 

 it is in fact most in accordance with the mode of occurrence of 

 vertical veins : at many points the direct contact is so exposed, 

 of the granite or syenite on the one side, and the transition 

 strata on the other, that we can convince ourselves tbat the 

 massive formation, on the zohole, neither lies over nor under the 

 adjoining strata, but stands at their side and cuts them off. 

 The continuity of the masses downwards can moreover be 

 pi'oved in the clearest manner by this, that in many places at 

 the boundary of the transition-formation, where, as we have 

 said, the Neptunian strata are no more to be found, we can 

 observe granite or syenite in conflict with the primary basis, 

 inasmuch as the latter is penetrated by the former, so that it is 

 clear that these granitic masses rise up from the very founda- 

 tion of the transition strata. Both in the primary series and in 

 the superincumbent formation, there are numerous branches 

 shooting from the main masses into the contiguous rocks, and 



