OF THE PARALLEL ROADS OF LOCHABER. 
705 
caused by the action of winter snow and weathering,* which continued for a time 
afterwards, has formed a coating (6, fig. 14) that partially modifies the original angle. 
As the lake again fell to the next level, the slope below the water-level would 
undergo further modification, as, in consequence of the detrital bank being then again 
set in motion, another slide would commence at the water-level, and carry down a 
portion of the detritus on this slope to a lower level, either to form another shelf if 
the waters received another check, or en masse to the bottom of the valley if no check 
occurred and the lake were drained. In fig. 11, n b" represents the slope formed on 
the second or subsequent lowering of the lake-level, by the slide of this segment d". 
On those short portions of the “roads” over which I walked I met with no natural 
section, excepting one 4 feet deep in angular debris and clay ; and the only published 
section I know of is the one which accompanies an interesting paper by the Rev. Thomas 
Brown, describing the discovery of Diatoms in the interior of the “ roads. ”t Fig. 12 
is a reduction from the original woodcut accompanied by the author’s description. 
Fig. 12. 
b 
Section of the lowest terrace (“road” No. 4), Gilen Roy. 
a. Humus, 8 inches to 1 foot. b. Stones with clay, 2 to 3 feet, 
c. Finely stratified sand and clay, 3 to 8 inches. (Diatoms found in centre of bed.) 
cl. Clay with boulders indistinctly stratified with thin layers of sand going down to 
rock (r), about 20 feet. (Diatoms found in this bed 10 feet below the surface.) 
This section is situated about midway in the Glen and on its west side. 
Fig. 13. 
a. Humus. b. Gravel and sands (c clay P) of the “road.” c. Underlying gravels and sand. 
e. Line of unconformity. 
m. Clay with boulders, most of them small (boulder clay ?). r. Rock. 
Another section! (fig. 13) discovered by Mr. Brown on the opposite or east side of the 
valley, but whether of the 3rd or 4th “road” is uncertain, presents features somewhat 
* This is the action which now takes place on the shore of the Merjelen See, and which has there 
formed the beach line. See also on this subject “ Observations on the Parallel Roads of Glen Roy,” 
by Professor Babbage, in the Quart. Journ. Geol. Soc., vol. xxiv., p. 273. 
t Proc. Edinb. Roy. Soc., vol. viii., p. 337, 1874. In the original paper the underlying rock r is not 
shown. This addition, together with the unpublished sections figs. 13 and 16, are from notes kindly 
communicated to me by Mr. Brown. In fig. 13 I have altered his d to m. 
I This section not being taken with a view to publication, the beds and angles were not measured. 
4x2 
