202 GEOLOGY OF ARRAN. 



enter it nearly at right angles. First, a vein of hornstone 

 six to eight inches wide; next, one of basalt five feet wide. 

 Another vein running a little N. of W. has on its north side 

 three feet of pitchstone, passing into hornstone, then four to 

 six inches of claystone, and on the south side fifteen feet of 

 basalt or fine greenstone. Next is one thirty feet wide 

 running N. 35 W., consisting of basalt four feet, clay- 

 stone fifteen feet, basalt again six feet, containing a pitch- 

 stone vein along its middle part; lastly, a vein of greenstone 

 five feet wide. There is here also a vein of trap porphyry 

 four feet wide ; this and the others intersect the pitchstone 

 vein, but the intersection is obscured by debris. The last vein 

 northwards is one of pitchstone with hornstone and jaspery 

 quartzite, running oblique to the shore, and varying from 

 eleven or twelve to thirty feet. Just outside the tideway it 

 meets and enters the great pitchstone vein, which, in its sweep 

 north, has reached this point, ranging now N. 10 E., and 

 at the junction there is nothing visible but claystone, which 

 forms the flooring at the common point of union. The two 

 veins unite here; and the joint vein continues its course 

 under masses of sandstone, but is not seen in the cliff aloft, 

 nor can it exist there. Still farther north, near where the 

 cliff ends, we noticed a pitchstone vein running E.N.E., 

 seven to ten feet wide, and visible in the cliff above; and 

 this appears to be the same vein continued. The close 

 association of so many igneous rocks is extremely curious; 

 we may either suppose the various products to be cotempor- 

 aneous, so that different rates of cooling and varying chemical 

 composition may have produced the differences now observ- 

 able ; or we may ascribe them to successive eruptions taking 

 place under varying conditions. Professor Jamieson was 

 the first to describe this interesting locality, which he does 

 with great fulness and accuracy. He gives also a figure 

 illustrating the position of the secondary or cross veins (Min. 

 of Scot. Id., vol. i. pp. 17 and 102). 



The following analyses of the claystone and pitchstone 



