642 D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER. 
I can see no better explanation than this, that originally these valleys had 
been filled up with drift, and that the same agent which spread the gravel, 
brought the boulders. At this time there was an open kyle or passage 
at the head of Glen Gluoy, and through which a current could pass. After 
the sea subsided to a level below 1000 feet, a lake was formed here, as in other 
elens ; and as these lakes subsided from one level to another, much of the 
drift was washed away, leaving the boulders exposed, and putting them into 
positions which they had not originally. 
Several boulders were noticed by me, standing in a very unstable position. 
Thus, there is one on the south bank of Loch Treig, as shown in fig. 16 (page 
630). A is a bank of detritus, the top of which is about 40 or 50 feet above the 
lake B. The upper part of A consists of white sand, horizontally stratified, 
formerly a bed reaching back to the rock of the hill C, distant about 50 feet. 
The breadth of this sandy plateau may be about 30 feet. It is broken down 
by rabbits next the lake, whereby a depth of several feet of sand is exposed. 
The boulder D stands upright in the sand bed, about 5 feet above its surface, 
and is about 2 feet thick How much of the boulder is buried in the sand- 
bed I had not time or means to discover. Its appearance suggested the 
idea that it had been floated on ice, and slipping off with one end foremost, 
sunk into the sand, then the bottom of a lake or sea. 
In reference to the direction of that general movement which seems to have 
passed over this district, causing a transport of boulders and gravel, one or two 
specific facts may be added. 
In the Ault Laire valley, situated about a mile to the west of Loch Treig, 
I found a number of red porphyry boulders. Several boulders of the same 
rock I found on Craig Dhu and Craig Coinnichte. I see that Mr Jotty 
supposes that these may have been brought by the Loch Treig glacier. I am 
not aware of any rocks of that description being 7m situ in any part of Glen 
Treig ; but they exist on Ben Nevis. I saw them there zm situ on the east side 
of that mountain.” 
The next fact which I mention was made known to me by the late Mr 
ANDERSON of Inverness, a geologist of great intelligence and experience. He 
informed me that among the gravel of the hill of Torvane, situated at the east 
end of the Great Glen, there are numerous pebbles and boulders from a con- 
glomerate rock existing 7m sztw near Fort Augustus (80 miles to the west). 
There is a huge boulder on the hill situated on the north side of the Linnhe 
Loch, opposite to Fort-William. It is on the west side of the hill, and ata 
height of 1494 feet above the sea. It appears to have been brought from the 
* Mr Jotty informs me that red porphyry rocks occur on the hill called Ben Dearg, so called 
from its red colour. Ben Dearg is distant some miles from Glen Treig, to the west. 

