Ch. VIII.] THE GRANITIC AND SCHISTOSE ROCKS. 155 



granite, whether of the main mass or veins, cannot be easily 

 separated : indeed, it is not always easy to determine where 

 one begins and the other ends ; and even then, a difference 

 of colour is the only mark of distinction. It would have 

 been desirable to have introduced these lines into the plan, 

 but they would have confused the details, unless drawn on a 

 large scale. 



The granite, at the junction, throws out several small veins, 

 which, however, scton terminate; and in one instance, as at 

 A, the vein runs through both granite and slate. At B, a 

 quartz-vein occupies the line of junction, and is intimately 

 connected with the rocks on either side. 



The granite-vein c commences in small branches from a 

 confused mass of an intermediate nature between granite and 

 slate, of which there are several others in its vicinity. After 

 a short course, these branches terminate in one vein four 

 inches wide, which is soon after traversed by a large quartz- 

 vein, by which it is diverted from its course 2J feet towards 

 the north; it again gives off more branches, which are 

 variously affected by small quartz- veins ; and, at last, all 

 gradually dwindle into mere threads, after a course of about 

 60 or 70 feet : on the same line, a few remote and irregular 

 bunches and strings of granite occur in the slate. The 

 southern branch of the vein c turns toward another vein of 

 granite, D, which begins on the eastern side of a little quartz- 

 vein, but not in contact therewith. At first, its course is 

 marked only by short branches, or merely by a different 

 appearance of the hard compact slate, for about 10 or 12 feet; 

 it then becomes well defined, is 8 inches wide, and gradually 

 increases in size to 1 1 inches, when it meets with a quartz- 

 vein, M, by which it is heaved 3 feet towards the north ; after- 

 wards it continues in the same direction, being 1 foot in 

 width, for about 30 feet, when it is heaved towards the south, 

 2 feet, by another quartz- vein ; and may then be seen run- 

 ning under the sea for more than 100 feet, apparently in- 

 creasing in size. The granite-vein E may be traced from 



