on the Bocks in the Environs of Edinburgh. 313 



Loch, in Dumbartonshire, I have found, as they did, that the 

 valley which ascends from the extremity of the bay to the 

 ridge which separates it from Loch Long, furnishes moun- 

 tain rocks, polished and striated, as well characterised as 

 those of the most celebrated of the Swiss valleys in this par- 

 ticular. To deny that a glacier occupied that valley would 

 not be more discreet than to deny that of the Aar at Nivele, 

 that of the Handeck, and the Hellenplatte. 



In the neighbourhood of Edinburgh the direction of the 

 streaks presents a difficulty which I wish in no degree to 

 depreciate. Upon the Pentland Hills, and in some other 

 localities to the south of the town, the striae are directed 

 from the west to the east, and at first sight one might be 

 tempted to believe that they should have been from north- 

 west to south-east ; in other words, from the mountains to- 

 wards the plain. In studying the large map of Scotland by Mr 

 Arrowsmith, and comparing it with the direction of the striae 

 indicated by Messrs Maclaren and R. Chambers, we may 

 explain what they effect to the south of Edinburgh. A great 

 glacier issuing from the groups of Benledi, of Benehochan, 

 and of Benclach, and thence turning eastward from Benlo- 

 mond, descended first into the valleys of the Forth and the 

 Teith, followed the direction of the Forth, and covered all 

 the country which surrounds the Frith of Forth from Stir- 

 ling to Edinburgh. Upon both sides of the Frith, the direc- 

 tion of the striae indicates that of the glacier, which advanced 

 from north-west to south-east, as does the Frith itself. But 

 another glacier, not less powerful, descended, turning west- 

 ward from Benlomond, from Benunack, Benlochen, Benvaigo, 

 and Benviolay, and filled, as the direction of the striae will 

 still teach us, the depressions of Loch Lomond, of Loch Long, 

 Loch Goil, and of the Gare Loch ; then it spread itself 

 over the plain of which Glasgow occupies nearly the centre. 

 But in this plain it would encounter the great glacier of the 

 Forth, and push it towards the east ; and hence this direc- 

 tion from west to east of some of the groups of the striae 

 to the south of Edinburgh. Existing glaciers follow the 

 course of the valleys ; ancient glaciers did the same ; and 

 when two glaciers of unequal force encountered each other, 



