J52 ASSOCIATIONS OF [Ch.VIII. 



becomes here of a finer grain, with black mica, and light 

 flesh-red felspar. On the north it laps over the schistus. 

 At this spot, numerous granite-veins, varying in width from 

 about a foot to less than an inch, pass through the slate ; the 

 two principal veins proceed nearly east from the hill above, 

 for more than fifty yards, until they are lost in the sea. One 

 of these, not far from its first appearance, is divided and heaved 

 several feet by a cross vein, consisting of quartz intermingled 

 with slate ; fragments of slate appear also in the granite- veins. 

 The most remarkable vein, after proceeding vertically for some 

 distance, suddenly forms an angle, and continues in a direc- 

 tion nearly horizontal, having slate above and below." * 



Oeynhausen and Dechen published, in 1829, an account of 

 their observations on the junction of the granite and the 

 killas rocks in Cornwall f, in which is a long and circum- 

 stantial description of that at Mousehole, illustrated by a 

 sketch. We have already described the large vein ten feet 

 wide as an elvan-course, following Mr. Carne, who has thus 

 denominated a similar large vein at Forth Just, though, 

 in fact, no distinction can be drawn between these forms of 

 the granitic rocks ; for there is a most perfect gradation, as 

 to size, regularity of figure, and position, from a well marked 

 elvan-course to the smallest granite-vein. On comparing 

 Oeynhausen and Dechen's plan of this vein with ours in the 

 fourth chapter, they will be found to differ much in their 

 bearings ; and that their plan does not exhibit the heave, is 

 very probably owing to their having visited this place at neap 

 tides, for which reason they have also not noticed a similar 

 phenomenon in the other granite veins which occur near 

 low-water mark. It may also be observed that, according to 

 these geologists, " the vein c is distinctly to be seen coming 

 but from the main body of the granite, which is as fine- 

 grained as the vein itself." That it may be so connected, is 



* Geol. Trans, of Cornwall, vol. i. p. 27. 

 f Philos. Mag., or Annals, vol. v. p. 161. 



