132 



2. On the Parallel Roads of Lochaber ; with Remarks on the 

 change of relative Levels of Sea and Land in Scotland, and 

 on the Detrital Deposits in that Country. Part II. By 

 David Milne, Esq. 



The authoi' proceeded to shew that the lake theory of the Loch- 

 aber shelves was not inconsistent with any established geological 

 truths, but was on the contrary supported by them. 



He alluded to the occurrence in the Lochaber district, as well as 

 in other parts of Scotland, in valleys far from the sea, not only of 

 lakes at high level, but of beach lines on hill-sides precisely analo- 

 gous to those of Glen Roy, and shewing depressions of water to nearly 

 the same extent. One of the localities referred to is a valley near 

 Inverournan, where three parallel roads are to be seen shewing a de- 

 pression first, of about 197 feet, secondly, of 94 feet, and lastly, of 

 1 84 feet. The blockage required for this ancient lake, and of which * 

 a small remnant still exists, was nearly as extensive as that I'equire ' 

 for Glen Roy. 



Other localities were pointed out where parallel roads on hill- 

 sides, similar to those of Lochaber, were to be seen. 



In corroboration of the existence of lakes at high levels which no 

 longer exist, reference was made to the existence of River Haughs 

 at considerable heights above the present course of the rivers. 



The author pi'oceeded next to shew, that when the rivers ran in 

 these higher channels, the sea stood at a higher level than at present. 

 He, in proof of the former submergence of the land beneath the waters 

 of the ocean, and its gradual emergence from it, referred, 1st, to 

 the occurrence of marine remains at considerable heights above high- 

 water mark ; 2d, to the existence of extensive sand-banks which 

 could have been formed only at the bottom of a deep sea ; and, 3d, 

 to lines of ancient sea-cliflfs and terraces along the coast. 



The author alluded next to the nature of the deposits formed, 

 when the land was covered by the sea, and endeavoured to shew, that 

 during this period the boulder-clay had been transported by some 

 great oceanic movement whereby the valleys were filled with detritus. 

 He shewed that the detritus had come from the westwai'd, and, there- 

 fore, that valleys situate, like those of Lochaber, on the east side of 

 lofty mountains, would be especially liable to be blocked up by de- 

 tritus. 



Reference was made to a number of boulders resting on beds of 



