54 ON THE PARALLEL ROADS 



the subsequent deepening of the present mouths of the glens, 

 bv means of their rivers alone, it is unnecessary to suppose at 

 present, that the barrier was destroyed by the second subsi- 

 dence of Loch Roy, to a depth much under that which was 

 merely necessary to reduce Loch Roy to the level of Loch 

 Spean, of which it now became an immense arm, as represent- 

 ed in Plate VIII. fig. 3. 



The consideration of what I suppose to have been the grand 

 cause which operated in producing the sudden and contempo- 

 raneous evacuation of the independent Loch Gluoy, and the 

 great, and by this time united Loch Spean and Roy, again 

 leads me to the Glen-mor-na-Albin, or Great Glen of Scot- 

 land. To those who have travelled throughout the extent of 

 this remarkable valley, it seems to me hardly necessary to 

 point out the various circumstances that lead to the supposi- 

 tion of its being an immense rent across the island, produced by 

 some extraordinary and powerful convulsion. Indeed the whole 

 of its appearance is more strikingly convincing to the eye when 

 examined, than any detailed description can be to the mind, 

 however minutely conveyed in words. But if we consider the 

 vast depth of its lakes, — the almost rectilineal straightness of 

 its direction, — its uniform narrowness, — the uniformity also 

 of the general shape of the abrupt and ' lofty fronts of its 

 bounding mountains, — the seeming adaptation of those on op- 

 posite sides to each other, — the wonderful equality of its level 

 from one sea to the other, — and the lowness of its summit-le- 

 vel, — which, as it is composed of vast beds of alluvial matters, 

 must have been even raised by time greatly above its original 

 state, — if all these circumstances, I say, be considered, it will at 

 least appear possible, that it may have owed its origin to some 

 such unusual event. But as I believe the evacuation of the lakes 

 to have been owing to no less magnificent a cause than this, I 



am 



