1863.] JAMIESGN PAKALLEL ROADS OF GLEN ROY. 239 



told strongly in its favour. This was the theory of Mr. Darwin *, 

 who urged it so forcibly, and handled so well the difficulties that 

 arose on every side when it was attempted to place barriers of earth 

 or rock in any of the required positions, that his explanation met 

 with general acceptance, and appears to be still the one most in 

 favour. 



A Swiss visitor, however, came and offered quite a new suggestion. 

 This was Agassizf, who, living in sight of the snow- clad Alps, and 

 awakened by the teaching of Yenetz and Charpentier to a perception 

 of the former vast extension of their glaciers, had much enlarged 

 our acquaintance with the ice -world, and had come over to Britain 

 to see whether he could find any trace of glaciers in a country where 

 none now occur. These traces he met with in abundance, and 

 nowhere more clearly than in Lochaber, which he visited in com- 

 pany with Dr. Buckland in 1840. Perceiving that the lines occupy 

 certain glens where the hills are comparatively low, and that ranges 

 of higher mountains encircle them on the W. and S. J, fronting the 

 opening of the valleys where the lines terminate, and that Ben 

 Nevis, the loftiest of them all (where the snow still lingers even in 

 the hottest summers), guards the entrance of the main valley, the 

 idea struck Agassiz that this curious phenomenon, that had puzzled 

 so many able heads, must be due to glacier-lakes, instances of 

 which were known to him in the Alps. Ice, in short, had been the 

 barrier that no one could find, and which, on the approach of a more 

 genial climate, had melted before the heat of the sun, and vanishing 

 left " not a wreck behind." 



Here was an explanation no one had thought of. The visit of its 

 author, however, was too hurried to enable him to work it out. 

 He merely pointed to the evidence of a former glacier having pro- 

 truded from Glen Treig across the valley of the Spean as one 

 element in the solution of the problem, suggesting that the ravines 

 of Ben Nevis would probably account for the rest. 



Admirably as this seemed to meet the difficulties of the case, yet 

 few were prepared to admit such a development of ice in this 

 country. Had the lines been in the Alps or the Himalaya, the ex- 

 planation might have been at once accepted ; but to suppose that 

 our little hills could have given birth to so large ice-streams seemed 

 to exceed all probability. Accordingly, though the parallel roads 

 have since been repeatedly examined by Messrs. Kobert Chambers § 

 and Milne-Home || ,and Professor Rogers, and although all three came 

 away differing with one another as to how they originated, yet they 

 agreed upon this point, that the theory of Agassiz was quite inad- 

 missible, — the two latter even declaring that no evidence whatever 

 existed of the supposed glaciers, at all events not in the places 

 where their presence had to be assumed. And it was pointed out 

 that the glacier from Ben Nevis, which Agassiz had laid down in his 



* Phil. Trans. 1839. f Edin. New Phil. Journ. vol. xxxiii. p. 217. 



X In the map accompanying this paper, the engraver has failed to bring out 

 this feature so distinctly as in the MS. sketch. 



§ Ancient Sea Margins, 1848. || Edin. Roy. Soc. Trans, vol. xvi. p. 395. 



