1855.] 



FORBES FOLIATION OF ROCKS. 



177 



Fig. 8. — Section at Lykkens Grube, near KrageroCy Norway. 



DC B 



X. Alluvium. a. Granitic gneiss. 



A. Granite ; b, c, d, e, granite veins. b. Ordinary gneiss. 



and gneiss, of undefined character ; and above is seen a small vein 

 of coarsely grained granite (b) containing numerous crystals of brown 

 titanite. The contorted structure of the foliation here observed is, 

 I think, due to the entrance of the granite-vein and the occurrence 

 of the granitic gneiss, v^hich seems in this case to be nothing more 

 than gneiss into v\rhich granite has infiltrated from large masses 

 of this rock, not seen in the section, but vsrhich are in the immediate 

 neighbourhood. 



Nov7 as to the influence of the intrusion of the igneous rocks on 

 foliation, it seems to me that the two are very intimately connected, 

 and that, in many cases at least, foliated structure seems to arrange 

 itself in planes connected with the configuration of the intruded or 

 underlying igneous rocks. 



Mr. Sharpe admits that the occurrence of such rocks has a very 

 disturbing influence on the regularity of his arches ; but it may be 

 fairly questioned whether such arches may not themselves be due to 

 the appearance or approach of such igneous rocks. 



Looking at Norway, we find no considerable tract of country 

 exempt from the constant occurrence of such igneous rocks ; and, as 

 far as my experience goes, these rocks seem generally to have an 

 apparent influence on the lines of foliation. 



Fig. .3 (p. 171) gives a good illustration of this; as also fig. 1 

 (p. 167) and fig. 5 (p. 173). 



(Case 14.) — Fig. 9 also represents a similar case at Pusaasen near 

 Christiansand, where we have a granite-vein (A) about 3 feet thick, 

 breaking through gneiss («) into crystalline limestone (c) similar to 

 that previously described, and foliated by augite, scapolite, and mica ; 

 below the small vein of granite (B), the gneiss (b) is more calcareous 

 and augitic ; but above, it is of the ordinary character, and does not 

 contain carbonate of lime. The strike is E. and W., and the dip 25° 

 to the South. 



VOL. XI. — PART I. 



O 



