IIh. Bktce on the Geological Structure of Roseneath. 123 



to me a few weeks ago by Mr. Robert Chambers, at Parson's Grreen near 

 Edinburgh. They resemble more the cases long ago described by Sir 

 James Hall, as ocsurring at Corstorphine hill and several other places 

 in the neighbourhood. 



III. — East Coast of the Cowal district. 



13. This coast consists of slates of the argillaceous and chloritic series, 

 passing westwards into mica slate. In the southern part, between Innel- 

 lan and Toward Point, old red sandstone, with its associated cornstone, 

 occupies the coast, extending, however, no farther inland than the terrace, 

 into the landward boundary or wall of which the slate rises to a consider- 

 able height ; but in neither the sandstone nor limestone have fossils yet 

 been found. The old slates near Dunoon are associated with rocks of 

 igneous origin, to whose effect upon the slates, and their own peculiar 

 forms, much of the picturesque beauty of this favourite watering-place 

 is due. Thus the ridge lying between the coast and the valley of 

 Hafton lake, owes its elevation and bold outline to an outburst of 

 igneous rocks, which have induced a very decided change upon the slate 

 along the planes of contact. It consists of crystalline gi-eenstone, of 

 a different type from that of the dikes common on the coast, the 

 structure being slaty and the hornblende in excess. It is from 

 60 to 100 yards wide, and ranges from near Hunter's Quay, across the 

 highest part of the ridge, transversely to its length, appearing along the 

 summit in a series of conical hummocks, with deep hollows between ; and 

 thus presenting a bold picturesque outline when viewed from the low 

 grounds in the neighbourhood. It is interrupted by the Hafton valley, 

 but is resumed on its western side, and attains its greatest altitude in 

 Dunloskin hill, which rises prominently above the surrounding slopes, 

 strikingly relieving their monotonous outline. Westwards, for about 

 half a-mile, it is seen in other rocky eminences, but its farther extension 

 in this direction was not traced. The ridge is not seen intersecting the 

 coast, which is everywhere occupied by the slate rocks ; so that it seems 

 to terminate before reaching the shore. Owing to the metamorphic 

 character which has been impressed upon the adjoining slaty beds, it is 

 diflicult to determine the precise limits of the plutonic rock ; near the 

 contact the slate breaks under the hammer into very compact four- 

 sided prisms. 



In a similar manner, the high ground dividing the East and "West 

 Bays, and projecting beyond the general line of coast, has acquired 

 its strikingly picturesque aspect from a great dike of basalt which 

 traverses it. The castle hill consists of this dike, and of slate borne 

 up with it, and adhering to it. By contact with the dike, the slaty 

 structure is effaced ; the rock has been fused and reconsolidated into a 

 compact flinty slate, closely resembling basalt ; crystals are developed 

 along the boundary, and bands of different colours are disposed parallel 

 to thesides of the dike. The width is about 100 feet, and the bearing 



