THE SCHISTOSE ISLES. 



to that of greenstone, and by the aspect of the surface, 

 which almost always resembles that of this rock even when 

 the composition is different. The rock of Cara, already 

 mentioned, presents this dubious character; but it is 

 infinitely more marked in certain parts of Loch Fine 

 which lie near the entrance of Loch Gilp. The vertical 

 prismatic fracture was also pointed out as occurring in 

 the grey ridge of Seil and Luing, which belongs to this 

 series. This rock, under its various modifications, is 

 the most conspicuous part of the series, and appears 

 to form nearly three -fourths of it; the quartz rock being 

 the next in quantity. 



That substance varies much in colour, being brown, 

 yellowish, white, 9r pale grey. It is sometimes compact 

 and crystalline, in others fissile, arenaceous, or so mixed 

 with mica as to present the appearance of micaceous 

 schist when split in the direction of the laminae. 



Next in order is common scaly chlorite schist, at times 

 arenaceous, at others silky, and either flat or minutely 

 undulated; but in all cases splitting into thin laminae, 

 and generally very tender where exposed to the air. It 

 is occasionally capable of being wrought for roofing slate. 



Common micaceous schist forms the last of the essential 

 beds of this series, being always flat and fissile, and 

 frequently presenting a greenish hue so as at length to 

 pass into the preceding rock. 



These two last beds rarely exceed a few inches in 

 thickness, and do not together seem to occupy a twentieth 

 part of the whole series. I may remark, in concluding 

 this enumeration of the essential and constant beds, 

 that in some parts of the region occupied by them, 

 the simple hornblende schist predominates over the 

 thick and compound chlorite schist, usurping in a great 

 measure its place in the series. This is more particularly 

 the case in Gigha, and about the point of Knap. 



It was already hinted that the usual order of ar- 

 rangement among these several strata, is that of a constant 



