OF THE PARALLEL ROADS OF LOCHABER. 
709 
Chambers also refers to a well-marked assemblage of similar markings on the 
hollow face of Craig Dhii on the north side of the Spean, above “road” No. 4, two of 
them being at heights of 1,055 and 1,167 feet.* Corresponding with two higher ones 
at 1,337 and 1,495 feet, he found two bold lines on Ben Chlinaig, on the opposite side 
of the valley. Elsewhere, in Glen Spean, he noticed lines below “road” No. 4, one 
at 750 feet and the other at 661 feet. He considered that an unbroken series of lines 
exists from the present sea-level up to the highest of the “ roads,” but was of opinion 
that they are all the result of sea action, and that these glens were once arms of the sea. 
Shelves have also been observed by Mr. Campbell on the south side of Loch Lagga.n, 
and he states that, in certain lights, several unnoticed water-lines become apparent in 
Glen Boy.t 
Captain White’s lines in Glen Gluoy may possibly indicate the height to which the 
water had risen before the rupture of the Turret barrier; and those of Chambers, 
in Glen Boy and Glen Gluoy, may indicate checks experienced by the water, owing 
to a variable resistance in the barriers as they yielded to the pressure of the lake waters. 
Weathering and vegetation have obscured and may have effaced many of these lines. 
[Since the reading of this paper, my attention has been directed by a notice in the 
Min. Proc. Inst. C. E. (vol. lv., p. 339), to a memoir, bearing on this question, of M. 
BENk Lefebvre’s, in the ‘Annales des Ponts et Chaussees,’ 5 me- ser., tome xvi., 1879, 
p. 390, “ Sur la Constitution des Terres, et sur les Accidents dans les Terrains 
Argileux.” In this paper the author discusses the cause and effects of slips on 
slopes formed of argillaceous soils, and he shows that, in the instance of a slip of an 
embankment, fig. 17* A, the slope assumed is that given in fig. 17* B. 
Fig. 17*, 
c, b. Original slope of bank, c', b'. Slope of land after the slip. 
The cases are not identical in origin, the cause of the slip in the original being due 
to a thin permeable seam at «, but the effects are, to a certain extent, analogous, 
inasmuch as the ledge c', U, formed by the slipped mass c, b, after heavy rains, is of 
similar form to that which we have shown would result from the slips on the slopes of 
Glen Boy, where they were due to the general permeation of the mass. 
* Some of these higher horizontal or quasi-horizontal lines are shown in Captain White’s sketches 
No. 3 and No. 4, but the lower ones there drawn are moraine mounds levelled by water action, 
t Op. cit., pp. 14, 15. 
