3Ik. Bryce on the Parallel Roads ofLochdber. 99 



XIII. — On the ParaUel Roads of Lochaber. By James Bryce, Jun., 

 M.A., F.G.S. 



I. — Introduction. 



The Lochaber glens have been subjected to so keen a scrutiny by the 

 advocates for the various theories of the Parallel Roads, that it cannot be 

 expected there should remain many facts of importance to be yet ascer- 

 tained. By this circumstance, however, the obligation upon an observer 

 at once to make known such facts as may have come under his notice is 

 rendered more imperative, while the value of new facts is enhanced. 

 Observations, which in other circumstances would be scarcely deemed 

 ■worthy of record, become of importance when viewed in connexion with 

 an inquiry such as this, which, after all the discussion elicited by it, still 

 remains the great unsolved problem of Scottish geology. In submitting 

 the following communication, it is not my purpose to advance a new 

 theory. I have merely in view the much more humble object of putting 

 on record a few facts, which seem to have escaped the notice of pi'evious 

 observers ; and of offering, in connexion with these, some remarks on the 

 two theories last proposed. I refer to those of Mr. Chambers of Edin- 

 burgh, and Mr. James Thomson of Glasgow, both published early in 

 1 848 ; the latter immediately before my visit, which took place in July 

 of that year. My examination of the district had thus additional interest 

 given to it, as the facts were to bo viewed under a somewhat novel aspect? 

 and had not yet been commented on by any geologist, with reference to 

 their bearing upon the two theories in question. 



Before proceeding, however, to remark on these theories, it will be 

 necessary to state the principal facts which have been ascertained 

 respecting the Parallel Roads. 



n. — Abstract of Facts. 



The Parallel Roads are shelves or terraces on the sides of certain glens 

 in Lochaber, perfectly parallel to one another and to the horizon, through- 

 out their entire course, and at exactly the same height on opposite sides 

 of each glen. They conform to all the windings of the hill slopes, their 

 continuity being broken only by rocky projections, and by the lateral 

 streams. The breadth is various, generally from 8 to 10 yards, in a few 

 rare cases reaching to 18 or 20, owing to the peculiar form of the ground ; 

 but the precise width is difficult to ascertain, in consequence of the outer 

 edge of the shelf being rounded off towards the valley. There are five 

 principal shelves in the district, besides some minor ones. They are most 

 distinctly marked in Glen Hoy and Glen Gluoy. There are three in the 

 former glen and two in the latter. The upper shelf in Glen Gluoy is 

 called No. 1, and the highest, middle, and lowest in Glen Roy, No. 2, 

 No. 3, and No. 4, respectively. The second Glen Gluoy shelf having been 



