

MR MILNE ON THE PARALLEL ROADS OF LOCHABER. 399 
A small rivulet trickles now among the rocks, infinitely too feeble to have 
produced the appearances. 
It is now, therefore, established, not only that the whole of the 4 shelves of 
Lochaber are coincident with water-sheds respectively, but that a great body of 
water had filled Glen Glaster, and of course Glenroy, the outlet of which was 
down this ancient river-course to shelf 4 in Loch Laggan, which is at a lower 
level by 212 feet. 
Whilst on this subject, I may mention farther, that I examined narrowly the 
interval of space between shelf 1 at the head of Glen Gluoy, and shelf 2 at the 
head of Glen Turret, where the last shelf is nearest to Glen Gluoy. This space 
also appeared to me to exhibit the features of an ancient river-course, though they 
are not so striking as those just described. The distance from the one shelf to 
the other, is about a mile. Where the Glen Gluoy shelf ends, rocky knolls rise 
above the moss, water-worn below the level of the shelf, but rough above that 
level. Their smooth faces are all towards Glen Gluoy. Near shelf 2, in Glen 
Turret, the rocks have evidently been excavated and cut into by some considerable 
stream ; at present a very small burn runs in this rocky channel, quite inca- 
pable of producing the appearances. 
The grandest exhibition of an ancient and deserted river-course is, however, 
at the head of Loch Laggan. The Pass of Mukkul is a channel, the bed and sides 
of which are entirely rock. It is, at its narrowest part, about 70 feet wide, the 
wall faces being on each side from 40 to 50 feet high. The rocks at the sides are 
evidently water-worn for about 30 feet up. To the eastward, this gorge expands 
into a broad channel of several hundred yards in width, divided in the middle 
by what has formerly been a rocky islet, against which the waters of this large 
river had chafed in issuing from the pass. For nearly a mile towards the east, 
the rocky banks continue on each side, but they gradually diverge, having between 
them a mossy fiat sloping gently eastward. The smooth faces of the rocks with- 
in the probable reach of the river-waters, are all towards the west, where Loch 
Laggan is situated. The height of shelf 4 above the highest point of this deserted 
channel, is, by barometric measurement, about 21 feet, which affords, therefore, 
some probable estimate of the average depth of the river. I have only to add, 
that no stream whatever now occupies this water-course, except where, for a short 
part of it, the river Pattaig flows in a reverse direction into the head of Loch 
Laggan. This stream was, when I visited it last September, only about 18 inches 
deep and 30 feet wide, and must be quite inadequate to have formed the rocky 
banks on each side of it. 
The ancient river-course now described is of much greater size than that at 
the head of Glen Glaster, just as the Glen Glaster river-course is of greater dimen- 
sions than those respectively at the head of Glen Gluoy and Glen Roy. The rea- 
son is obvious. The river at Mukkul had to discharge not merely the waters 
VOL. XVI. PART III. 51 
