272 CRAIGNISH ISLES. GEOLOGY. 



quent transitions ; the thicker beds, which are those of the 

 compound chlorite schists and quartz rock, being: separated 

 by the thinner micaceous schists and by other varieties of 

 chlorite schist of a finely laminar structure. They are all 

 remarkable for their evenness and regularity; never pre- 

 senting those irregularities and contortions so conspicuous 

 in micaceous schist, and which are of general occurrence 

 in the western chain that extends from Lunga to Isla. 



The circumstances under which the veins of trap are 

 found, here and on the adjoining coast, are interesting. 

 After passing Killean, on the coast of Cantyre, they 

 almost entirely disappear in proceeding northwards. 

 About the point of Craignish they again commence, and 

 are to be observed in great numbers along this shore ; 

 increasing in frequency as we approach the great mass 

 of trap that occupies so large a part of Lorn, and is 

 connected with that of the Slate isles and of Mull. They 

 present numerous examples, often highly picturesque, of 

 those features formerly described as characterizing them 

 in Mull and in some parts of Sky. The walls often project 

 on the shore far from the surrounding cliffs of the strati- 

 fied rocks, sometimes attaining the height of 100 feet, 

 and being generally vertical with parallel sides. The 

 artificial appearance they hence present, is much increased 

 by the transverse prismatic fracture so frequent in trap 

 veins, which gives them the appearance of masonry; 

 while their resemblance to the ruins of castles is com- 

 pleted by the ivy that creeps about them, affecting pecu- 

 liarly this situation, as it is a plant otherwise very uncom- 

 mon on the western coast. 



These examples may be added to others formerly 

 adduced to prove that the prevalent trap veins of the 

 western coast of Scotland, are processes diverging from 

 the great masses so conspicuous in this part of the island. 



