TWO GLENS AND THE AGENCY OF GLACIATION. 197 



intrusive material, these for the most part being a porphyritic granite. As the Mica 

 Schists include not merely beds of mica slate but beds also of quartzite and of limestone 

 and of a material which has been suspected to be stratified volcanic ash, there is ample 

 room for the agencies of denudation to do a good deal of differential work — quite capable 

 of accounting for many different aspects of the surface. Moreover, as the sedimentary 

 beds are all more or less inclined at a high angle, glens cutting through them are liable to 

 have sides or walls, some of which present the slope, and others the escarpment sides of 

 the strata, according to the direction in which these are traversed. But if due attention 

 be paid to those causes of a certain amount of difference in the scenery, we can easily 

 separate them from other causes which have operated in other ways. In the case of these 

 two glens there are some special differences which are very striking. The separating wall 

 of mountain is common, of course, to both glens, and the two other, containing ridges to 

 the west and east respectively, rise to about the same elevation, and consist very much 

 of a repetition of the same, or closely similar beds. Yet, in spite of their close structural 

 resemblance, the two glens present a violent and curious contrast to each other. The 

 mountain slopes on either side are as steep in the one glen as in the other. But in Glen- 

 shira they are comparatively smooth and regular in surface, showing the slopes and 

 escarpments on either side clearly, and unencumbered by rough knolls or lower ranges of 

 hill. The bed or bottom of the glen is still more remarkable in the same way. It is a 

 smooth and level valley, occupied by a rich alluvial soil, and running about four miles 

 from the sea before its river reaches the elevation of 100 feet. Its placid, peaceful, and 

 rich pastoral character is very beautiful — but singularly unlike most other highland glens, 

 and reminding us more of the glens and valleys in Westmoreland. Glenaray, on the 

 contrary, on the other side of the same dividing ridge, is in every respect different — it 

 is a typical highland glen, occupied by a rapid brawling river, which plunges over 

 three successive waterfalls and runs the rest of its course down a bed encumbered with 

 stones and rocks. The whole surface of the glen partakes of the same rough and 

 irregular aspect. Along the lower slopes near the river, it is encumbered with enormous 

 quantities of loose stones of every size and shape — some of them of gigantic proportions, 

 and most of them quite unworn and unrounded, — presenting, on the contrary, many sharp 

 angular surfaces. Farther up the glen its floor is largely occupied by great conical 

 mounds of clay, sand and gravel, with a multitude of included stones. They represent 

 typically the boulder clay. Through many of these the line of the public road to 

 Dalmally, on Loch Awe, has been cut — showing sections which prove that these mounds 

 have generally not even a nucleus of solid rock, but are composed entirely of transported 

 materials from the grinding down of the rocks around. The included stones are strongly 

 smoothed and striated — very fine specimens of polishing and striation being common in 

 the sections. In short, the whole course of Glenaray is a conspicuous example of the 

 most characteristic glacial action — of a very marked and violent kind. One side of it — 

 the eastern side — presents a surface of moor full of knolls and mounds all covered with 

 loose transported stones, and rocks of every size and shape. The escarpment to the 



