24 



GEOLOGY OF ARRAN. 



to the same period of disturbance. But as the granite of the 

 nucleus is nowhere seen to alter the carboniferous formations, 

 while it certainly does, as above stated, alter the old red 

 sandstone, it is quite possible that these carboniferous strata 

 may have been deposited upon the old red sandstone during a 

 period subsequent to the irruption of the granite. But this 

 irruption took place in hypogene depths, not only prior to 

 the elevation of the island above the waters of the primeval 

 ocean, but while the granite was yet enveloped by the 

 mantling slate rocks, and perhaps also by the later forma- 

 tions, as shewn in the annexed cut (fig. 7), in which a is the 

 granite yet enveloped by the slate; b, slate; and c, conglo- 

 merate, with slate fragments, but none of granite. It is 



a Fig. 7. a- 



a a, Granite; 6, slate; c, old red sandstone. 



obvious, as already pointed out in Art. 9, that these secondary 

 strata have not derived the detrital materials of which they 

 are made up from the disintegration of the granite ; this rock 

 was yet protected from disintegration by its mantle of slate ; 

 and the Old Red derived its materials from other, and some 

 of them remote sources. An extensive disintegration and 

 denudation may even have gone on for a long period, ere yet 

 the strata were injected by the melted granite; for in several 

 places the conglomerate, partly made up of slate fragments, 

 is altered as well as the underlying slate ; and besides, 

 the extreme narrowness of this band on the east renders' it 

 very improbable that portions of the injected veins, with 

 adhering slate, should not be found in the conglomerate, if 

 the injection had been prior to the denudation and to the 



