Glaciers and Icebergs in Scotland. 127 



a? is a vein of reddish compact felspar, which projects con- 

 siderably above the slate, and seems to terminate at its east 

 end in a vein of greenstone. It is from 5 to 10 yards in 

 breadth, nearly half a mile in length, and is porphyritic, con- 

 taining embedded grains of white felspar and scales of black 

 mica. 



^ is a vein of fine-granular greenstone, 12 or 15 yards in 

 breadth, lying conformably amidst the slate. There is ano- 

 ther some miles eastward, also on the south shore of Loch 

 Long. 



z. Very near the greenstone are three veins of brown or 

 reddish compact felspar, each about 5 or 6 feet broad, and 

 crossing the laminae of the slate. Such veins are rare on 

 Oare Loch , if they exist ; and their seeming abundance here 

 (for as I did not examine the shores of Loch Long, and stum- 

 bled on these by accident, the presumption is that there are 

 many more) is a fact worthy of notice, as indicating that 

 disturbing causes have operated at the locality, to which 

 perhaps the deep and narrow fissure of Loch Long owes its 

 existence. 



On the eastern margin of Gare Loch, from the wooden 

 quay at h to the angle at i, where the bay widens out, along 

 a space of five or six furlongs, the striae are seen at every 

 spot where the slate is tolerably compact, and in characters 

 too distinct to be mistaken. The rock is everywhere exposed 

 here on the beach, or on the sea cliff behind it. The planes 

 of stratification run across the bay (in the direction of the 

 parallel shading lines) ; and the laminae of the slate, which 

 dip to the south at 50 or 60 degrees, present their edges to 

 the water. The striae (using the word comprehensively for 

 scratches, flutings, and groovings) cross the laminae nearly 

 at right angles, and there is no danger of mistaking them 

 for natural inequalities of any kind in the surface of the 

 rock. They point invariably SSE., that is, they are parallel 

 to the axis of the loch. The striae are seen sometimes on a 

 horizontal surface, where they must have been produced by 

 tiiie weight of an incumbent mass, sometimes on a vertical 

 surface, where they must be due to lateral pressure ; and at 

 this locality they are of all sizes, from a small scratch to a 

 gi'oove nine inches broad. Elsewhere they are much larger. 



