276" St. CORMAC's ISLES, &C. GEOLOGY. 



like the Slate isles and those of Craignish. Their di- 

 rection is pretty accurately north-east, and in this . respect 

 they correspond very exactly with the strata of the adjoin- 

 ing mainland. The predominant rocks are, as in the 

 Craignish isles, chlorite schist, micaceous schist, and quartz 

 rock ; together with certain anomalous substances which 

 will be described in detail hereafter. They present also 

 the same alternations, with the same regular distribution 

 that will be found to pervade the whole of this series. 

 Among them is found a thick bed of limestone, which 

 Occupies nearly one half of the breadth of the island, 

 or rather, one half of the breadth of the strata. Like 

 the rest, it is vertical, and is generally of a pale or dark 

 blueish grey, having in some places, portions inter- 

 posed of a red colour. Its texture is between the 

 granular and crystalline, and in some parts lax and are- 

 naceous. This bed is not found in Isla, since the di- 

 rections of these strata, prolonged to the south-westward, 

 do not meet that island ; but it occurs, as might be 

 expected from its bearings, in Dana, where it is of similar 

 dimensions and composition, and is accompanied by the 

 same strata. It is not necessary to give any description 

 of that spot, as the intimacy of its connexion with the 

 mainland is such, that it can scarcely be said to form 

 an island; being only separated by a narrow tide neck 

 from the adjoining shore. 



The smaller islands included under this title, present 

 strata occupying a similar direction, but with a dip de- 

 cidedly to the eastward; in which respect also they 

 correspond with the rocks on the mainland; since, on 

 this part of the shore, it will be found that the dips 

 decline from the perpendicular towards that quarter. The 

 substances found in them are, common quartz rock, an ex- 

 tremely dark micaceous schist composed of black mica 

 with a very small proportion of quartz, chlorite schist, and 

 a schist composed of chlorite and hornblende. 



The rocks and islands which lie close to the point of 



