256 R. Chambers, Esq.. on Glacial Phenomena 



where maintaining precisely one direction, and that from 

 NNW. To all appearance, the agent which produced these 

 impressions came over a lofty range of hills from Balquidder, 

 and passed on to cross a scarcely lower range, and descend 

 into the valley of Loch Ard. There has also been, as already 

 mentioned, an issue of glaciers by the south-east end of the 

 lake, among the defiles of the Trosachs, part of the rough- 

 ness of which is caused by a large moraine. 



The descent of this great or general glacier into the south 

 and east of Scotland can be traced at other points. A lofty 

 and extensive sandstone plateau between Campsie and Glas- 

 gow, exhibits extensive smoothings, with striation from 

 WNW. Eminences of trap in the valley of Strathblane 

 have manifestly abraded faces to the north-west. There are 

 clear marks of the passage of ice over the conglomerate skirts 

 of Demyat, directed to ESE. ; also, in the same direction 

 over the sandstone at the Tor wood, near Larbert. The line 

 of the remarkable passages through the trap eminence at 

 Stirling Castle is precisely conformable. Farther on, the 

 agent gets a turn to the northward, bringing it into con- 

 formity with the line of the Forth valley ; it continues to be 

 from about W. 15° S., all along by Edinburgh and East 

 Lothian, the only remarkable excess in this twist of movement 

 being at Silvermine quarry, a lofty position to the south of 

 Linlithgow, where it is as much as W. 45° S. On the lime 

 stone here, over beautifully marked surfaces, lies a deep bed 

 of the compact blue clay with blocks, which, besides being 

 scattered through the mass, form a zone a good many feet 

 down, a striking but not unexampled peculiarity. 



From the south of the Pentland Hills and Lammermuir 

 range, there are no reported examples of abraded or scratched 

 surfaces, a fact apparently to be attributed to the splintery 

 character of the Silurian hills of the south of Scotland. The 

 general mammillated character of the outline of these hills 

 is, however, very remarkable, from its resemblance to the 

 configuration of ground on which we trace true ice markings. 

 It is also to be noted that in Berwickshire, the masses in- 

 closed in the boulder clay are from the west.* 



* Mr D> Milne on Parallel Koads of Lochaber. 



