Dugald Bell — Notes on Glen Roy. o'23 



But, it is added, terraces of this kind "are only formed under 

 exceptional circumstances, and are accordingly local in occurrence " 

 (p. 98). This is just what has to be explained, and what we 

 think the " glacier theory " does explain. Can Dr. Bonney indicate 

 what exceptional circumstances, in the event of a submergence, 

 favoured the formation of these beaches in Glen Roy rather than 

 in Glen Gluoy, and in many other glens nearer the coast and 

 opening more directly on the sea ? Why, for example, should 

 these alleged sea-beaches not be found in the neighbouring Great 

 Glen, which, in the event of a submergence, must have been 

 powerfully acted upon by the sea ; as also in the Tay valley, the 

 Forth and Clyde valley, the Tweed, Annan, and Nith valleys, and 

 others ? We can see no answer to these questions. 



Noticing again the discrepancy between the terrace in Glen Gluoy 

 and the highest in Glen Koy, which " ought to agree " (the heads 

 of the glens being only a few hundred yards apart), instead of the 

 former being some 15 feet higher, 1 Dr. Bonney adds that "the facts 

 stated merely require that the land in rising should be tilted 

 slightly upwards towards the north, while it, remained nearly at 

 the same level towards the west" (p. 98). We are not aware that 

 the roads have been observed to rise towards the north, or are 

 appreciably higher in the upper part of the glen than in the lower. 

 All the earlier observers and surveyors dwell on their " perfect 

 horizontally " ; but we know that later measurements show certain 

 — after all, unimportant — deviations. Prof. Prest wich pointed out that 

 instead of a perfect level, the roads are " slightly waved," forming 

 partial "curves," there being a difference of a good many feet 

 between the highest and the lowest points of each, bearing a very 

 small proportion, however, to their entire length. " To all appear- 

 ances," he admits, "they are perfectly level." Sir Henry James, 

 the former Director-General of the Ordnance Survey, stated that 

 they "deviate slightly from horizontality in those parts where 

 streams from the mountains above have cut small watercourses 

 through them" 2 — which is just what might be expected. Indeed, 

 we think the marvel is that, in spite of the loose and sandy nature 

 of the material, these remarkable lines are still so perfect and so 

 nearly level. There is no evidence that we are aware of in favour 

 of any "tilting to the north," nor do we think that the sudden 

 difference of 15 feet between the terrace in Glen Gluoy and the 

 highest in Glen Roy, " only a few hundred yards apart," can be so 

 explained. Besides, Glen Gluoy lies to the icestward of Glen Boy, 

 where Dr. Bonney supposes the land to have " remained nearly at 

 the same level." 



The truth is that, while Dr. Bonney thus labours on these minor 

 points, a greater difficulty is all the time placed before him, 

 which he simply passes by — viz., the fact that each " road " coincides 

 with a col or opening out of the glen in which it occurs. Why should 



1 We may here repeat the figures as an aid to the reader's memory. Terrace in 

 Glen Gluoy, 1166 feet; those in Glen Roy, 1151, 1067, and 855 feet. 



2 Notes to the Survey Map of the district. 



