76 



morphic structure, firmly adhering to the slate, and intermingling and 

 interlacing with it, as if the slate had been forcibly injected among 

 the strata of conglomerate in a melted state. This interesting junc- 

 tion seems to have escaped notice, till observed by us, in the summer 

 of 1856. Something analogous, though less striking, is seen towards 

 the junction in the burn of the White water, above Corrie, where a 

 gradual passage takes place from slate to sandstone, clearly the effect 

 of metamorphism, by the heat to which both were subjected. The 

 facts clearly show the posteriority of the granite outburst to the 

 deposit of the old conglomerate, and that the entire slate stratum 

 on the east or Corrie side was in a plastic state, under the influ- 

 ence of the intense heat which fused the granite. 



Viewing all these facts in connection with the general conforma- 

 bility of the carboniferous strata to the old red sandstone, and the 

 gradual transition from the one series to the other, observed in seve- 

 ral places, there seems a great probability that the injection of the 

 granite, in a melted state among the strata, took place after the 

 deposit of the carboniferous formations ; and that therefore the gra- 

 nites of the three disconnected tracts may be all of one age, or belong 

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

 is nowhere seen to alter the carboniferous formations, while it cer- 

 tainly does, as above stated, alter the old red sandstone, it is quite 

 possible that these carboniferous strata may have been deposited 

 upon the old 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 formations. It 

 is obvious, as already pointed out in Art. 47, p. 69, 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 

 molten granite ; for this injection, we have seen, alters the conglo- 

 merate^ partly made up of slate fragments, through the medium of 

 the fused or semifused 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 con- 

 glomerate, if the injection had been prior to the denudation and to 

 the deposit of this latter rock. The elevation of the central granite 



