128 



THE RELATIVE POSITION OF THE 



[Ch. VII. 



each other endwise as at Mousehole ; but with this difference, 

 that the line of union is nearly perpendicular, corresponding 

 with the parallel fissures in the granite, which are clearly 

 seen to owe their position to one system of planes of the 

 rhomboidal concretions being placed upright. The other two 

 planes dip at different angles, and the strike of these beds de- 

 clines towards the nearest granitic headland; so that in 

 tracing the lines of structure through both rocks, they seem 

 to form the continuation of the same beds ; the eastern ends 

 being of granite, the western of slate. 



Fig. 8. 



Junction of Granite and Slate at Rosemodris. 

 (Cliff Section.) 



The junction at Forth Just, near Cape Cornwall, is simi- 

 larly circumstanced, though the appearance is more com- 

 plicated by the occurrence of a large metalliferous vein which 

 is situated precisely between the granite and the slate. This 

 vein, in the perpendicular section of the cliff, appears to form, 

 as it were, the end of a regular bed of rock corresponding 

 with the beds of the granite and slate on either side ; but the 

 lines of concretion are not regularly continued through the 

 vein : some slight indications of such a disposition are visible 

 at several points ; and that they are not more distinct, may 

 be attributed to the very compact and comparatively inde- 

 composable nature of this quartzose vein. The structure and 

 composition of this vein and the adjacent rocks will be con- 

 sidered more in detail in another chapter: at present the 



