135 
of Edinburgh, Session 1878 - 79 . 
from the JST.W. would strand more frequently on the central ridge 
and on the east side than elsewhere. If the valley was originally 
filled up to the level of the central ridge, the debris at its two sides 
must have been scoured out by the rivers now flowing through it ; 
and in this case, whilst the boulders in these parts would gradually 
find their way to the channel of the rivers and to the sea, the' central 
ridge would retain most of the boulders originally lodged on it. 
On this ridge the smoothed rocks face due H. and not IST.W. 
This deviation may be accounted for by the valley here being 
between two elevated ranges of hills running almost due north and 
south, which would cause the current to flow in a direction due south. 
One of the boulders on this central ridge measured 16x14x12 
feet, = about 200 tons in weight. 
It will be observed that on the S.E. side of A there is a large 
accumulation of boulders. These might have been floated there by 
an eddy occasioned by the projecting headland near A. 
5. Almost 1 \ mile to the south of Tarbert, there are several 
large boulders, on the east side of the high road leading from Tar- 
bert to Lach Castle. The Convener, on examining them, found 
them to be granite of a grey colour, whilst the rocks in the hills 
about them are gneiss. 
These boulders being within half a mile of the sea, which is to 
the eastward, and being at a height of about 100 feet above the sea- 
level, it might have been presumed that they could have come from 
the eastward. But these boulders were on hill slopes facing the 
west : and as the slopes were steepish, it was not easy to understand 
why, if the boulders had come from the east, they had not rolled to 
the foot of the slopes. On the other hand, there were towards the 
west and north, ranges of hills, reaching to heights above the level 
of the boulders, viz., to about 200 or 300 feet. But towards the jST.W., 
and at a distance of three-quarters of a mile, there was a gap or 
depression in the hill range; and, on applying the spirit-level, it 
was found that the depression was about the same level as the 
boulders, so that they might have come from that quarter by flota- 
tion, and been lodged on their present sites. 
Big. 27 is intended to represent what has just been described. B 
are the boulders, AAA a range of hills to the westward, with a gap 
in those at G, bearing H.W. from the boulders. 
