OF THE PARALLEL ROADS OF LOCHABER, 
719 
Irregularities of level, small as these are, could not exist in the shore-lines of quiet 
and narrow lakes. If the differences had been caused by subsequent movements of 
elevation or depression, all the “roads” would have been affected alike and the curves 
would have been similar and parallel, and not discordant. Therefore the variations could 
only be due to a cause influencing each case separately and independently, but in each 
case, nevertheless, the similarity of the effects indicates a cause of the same nature ; 
and if of the same nature, the conditions under which “road ” No. 3 was formed will 
be equally those which governed the formation of the other three “ roads,” and the 
explanation suited for that one will be applicable to all. 
That explanation was, that the rapid fall of the lake on the bursting of the minor 
barrier on the col led to a sliding or slipping down of the detritus on the slopes of 
the hill,* which continued until checked by the water coming again to rest on reaching 
the col level. A perfect horizontally of the “ roads ” is indeed hardly compatible with 
this hypothesis, as the momentum of the falling mass of detritus must have been 
greater or less according to the slope of the ground, and, slight variations of slope 
being frequent, small irregularities of level would naturally follow. 
There are, it is true, two other ways in which some variation of level might, if 
within certain limits, be accounted for : the one by a subsequent irregular subaerial 
fall of debris from the slope above, and the other from the circumstance that as the 
observations are taken in the centre of the “ roads,”t the inclination of which varies, 
so the height of the centre in relation to the inside edge of the “ road ” would vary 
accordingly. 
But there is nothing to connect the irregularity of the “ roads ” with irregular falls 
of debris which woidd be apparent by the greater talus at the foot of the slope; and 
the actual differences of level at the central points are too great to come within the 
limits of variation that arise from the differences of the angle of inclination. Taking 
the inclinations, apart from a few very exceptional cases, to vary between 5° to 25°, 
and the width of “road” to average about 50 feet, the difference arising from this 
range of variation in the angles would not exceed 8 or 9 feet, and, looking at the 
inclines more commonly met with, the difference would more generally be confined 
within the limits of 2 to 3 feet. This will therefore hardly account for “roads” 
Nos. 1, 2, and 3 being so often 10 to 14 feet below the level of the cols; while in 
those cases where the “ roads ” are above the cols, which they occasionally are to the 
extent of 4 feet, the difference due to the foregoing cause must be taken in addition 
to, instead of in deduction of, the apparent difference of level. No. 4 “road,” also 
is always from 2 to 14 feet above, and is never below the level of the Pass of Makoul. 
* Slides now occasionally take place after heavy rains. I saw one which had occurred a short time 
before my visit, on the side of the hill beyond Dalriach, on the east side of the glen. As well as I could 
judge at a distance, the fall had extended for a length of about 100 feet, and had left the rock bare. 
| The “roads” have no doubt been raised generally by subaerial debris, while the cols may also have 
been raised a few feet by the accumulation of soil since the lake waters passed over them, 
MDCCCLXXIX. 4 r A 
