422 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 16, 



rock, or softer vein of stone, may have determined the greater waste 

 in this place, still the time required for its formation must have been 

 enormous. It seems indeed almost impossible to estimate the num- 

 ber of ages spent by the waves in cutting out a cave of 130 feet in 

 length in a rock of such hardness as the porphyries of Davar Island*. 

 There are other indications of recent geological action in this lo- 

 cality which it is sufficient merely to mention. Many of the striated 

 boulders in the clays are apparently derived from a distance, and 

 some detached travelled stones are seen on the surface. Thus, near 

 Macharioch I observed several large boulders of white granite, one of 

 them measuring 5 feet by 4, and projecting 2 feet from the ground 

 in which it was partially buried. The stone resembles the granite of 

 Arran, which is the nearest place where this rock occurs in situ, 

 though at the distance of twenty-five miles across the deep hollow of 

 the Kilbrannan Sound. Striated rocks were noticed in several lo- 

 calities, of which the following were the most distinct : — 



Hill above Smerbie, on east coast, on claystone-porphyry. Direction 

 S. 55° E. In the line of a hollow to the sea. 



On the south road, east coast, near the third milestone, on claystone- 

 porphyry. Horizontal strise on a vertical face of rock. Direction 

 S. 55° W. 



On the south road, near the sixth milestone, striae on sandstone 

 newly uncovered. Direction E. 10° N. (by compass). This is 

 nearly parallel to the line of coast, and in the direction of Arran. 

 The north-east faces of the rock seemed the most highly polished. 



On the road, about four miles from the Lighthouse, the newly exposed 

 mica-slate was rounded, with indistinct striae, some running nearly 

 N. and S. along the valley to the sea. 



Some results of the examination of this little-visited portion of 

 Scotland appear of considerable interest in connection with the gene- 

 ral geology of the country. In regard to the oldest rock, or so-called 

 mica-slate, its most important peculiarities are its arenaceous, slightly 

 metamorphosed character and peculiar mineral composition, on the 

 one hand, — its anomalous direction and constant easterly dip on the 

 other. In a former communication to the Society f, 1 pointed out 

 the approximate parallelism of the great band of clay-slate and mica- 

 slate along the southern margin of the Grampians to the Silurian 



* Besides, we must take into account the portions cut away from the exterior 

 during the formation of the interior cave. The length of this cave marks, not the 

 total wave-action during the period of its formation, but the difference of this 

 action in the interior and on the exterior. The sea-cliff in which these caves 

 occur is no less strongly marked on the opposite shore of the Firth of Clyde, in 

 the Silurian rocks described by Sir R. Murchison. It is there also perforated by 

 caves, or cut by open fissures of enormous size, marking the long period during 

 which the sea remained at this level. It is remarkable, that, although several 

 supposed higher beach-lines have been pointed out, none of them exhibit either 

 the continuous line of cliff, or the numerous sea-worn caves of this 30-feet beach. 

 It evidently marks a period of longer pause in the upward motion of the land than 

 any former line — a pause also longer than the present has yet been. 



t Quart. Journ. Geol. Soc. vol. vi. p. 53 et seq. 



