1862.] JAMIESON GLACIATIOTs^ OP SCOTLAND. 173 



since the disappearance of the ice, is an excellent proof of the tough, 

 indestructible nature of the substance it had to work upon. Well 

 might Agassiz say of it, ''I do not believe that a locality exists, 

 where the facts indicate in a more special manner the cause which 

 has produced them." 



The River Spean, which receives the drainage of Glen Treig, runs 

 from E. to W. at right angles to the direction of the lake ; and just 

 opposite the gorge there is a mass of syenitic granite, forming some 

 low rocks that extend for some distance eastward. I^ow it is an 

 interesting fact, that this granite lying on the north side of Glen Spean 

 is, as Agassiz observed, " not only polished with that polish charac- 

 teristic of glacier-action, but is, moreover, scratched transversely — 

 that is to say, at right angles to the direction of the valley — by a 

 cause which evidently proceeded from Loch Treig." (Ed. Phil. Journ. 

 xxxiii. p. 238.) As the existence of these transverse markings has 

 been disputed, I am glad to be able to confirm the accuracy of the 

 illustrious Smss, and may mention that an instance of such marking 

 is to be seen on the north side of the Loch Laggan road, about 200 

 yards west of the thirteenth milestone from Loch Laggan Inn. Pro- 

 ceeding down Glen Spean, the striae (everjrwhere to be seen) are found 

 gradually to curve round from N. and S. until they finally assume 

 a normal east and west direction parallel to the valley, and at right 

 angles to their former course ; and along the road for four miles west- 

 ward, as far as the Catholic Chapel, the rocks are seen to be ground 

 down more especially upon their east side, and, where not too much 

 weathered, still showing the glacial scoring. Here I have to men- 

 tion an important fact that seems to have escaped the attention of 

 previous visitors ; and it is this, that from a point in Glen Spean 

 opposite the gorge of Loch Treig, all along the road to Loch Laggan, 

 glaciated rocks are to be found, showing the scores running parallel 

 to the valley, but it is now no longer the east, but the west, side of 

 the rocky masses that has sustained most abrasion ; and far away, 

 even for three miles to the east of Loch Laggan, I traced the same 

 appearances. Eor beyond the Pass of Makoul, the low rocky emi- 

 nences show evident traces of the passage of ice going out towards 

 the valley of the Spey ; as if at a point in Glen Spean, opposite the 

 gorge of Loch Treig, there had been an immense accumulation, 

 which had parted there and gone out in two great streams, one 

 taking an eastward route by Loch Laggan to the Spey basin, while 

 the other flowed west, down Glen Spean, to swell the mass of ice at 

 the mouth of the great Caledonian YaUey. 



The following are some striking facts that will help to give an 

 idea of the depth and volume of this great ice-stream. Glen Spean 

 is rather a wide glen, and, for some miles below the junction of the 

 Treig, is bounded on its north side by a considerable hill called Craig 

 Dhu, on whose flank the lowermost of the parallel lines of Glen Roy 

 is clearly marked. The bottom of the valley is here about 400 or 

 500 feet above the level of the sea, while the line is 847 feet, accord- 

 ing to the levelling of an engineer employed by Mr. Robert Chambers. 

 The top of Craig Dhu, by aneroid measurement, I made out to be 



