46 
BATHYMETRICAL SURVEY OF 
ing is 65 feet. At the head of this loch there is an alluvial flat that 
stretches westwards for 1^ miles, formed by the Lochlarig river and its 
tributaries. The gradual silting up, which is in constant progress at 
the head of Loch Doine at the mouths of the Lochlarig river and Allt 
Carnaig, is well shown by the resultant curve in the 50-feet contour-line. 
That Loch Voil is merely a continuation of the Loch Doine basin is 
further proved by the soundings, for immediately to the east of the 
cones just referred to, the 50-feet contour-line is met with, and has been 
traced round both sides of the loch eastwards to about Ledereich — a 
distance of about 2 miles. From this point eastwards the lake gradually 
shallows towards the alluvial flat at Balquhidder, where moraines occur 
within 400 yards of Kirkton and Stronvar Bridge. The deepest part of 
the lake is enclosed by the 90-feet contour-line at the head of the loch 
near Monachylebeg, and the deepest sounding within this line is 98 feet. 
The trend of Lochs Doine and Voil roughly coincides with the strike 
of the crystalline schists in that district. It is oblique — indeed, nearly 
at right angles — to the movement of the great ice-sheet during the 
climax of glacial conditions, and it harmonizes with the course of 
the later valley-glacier. Several small faults occur on the Braes of 
Balquhidder, north of Loch Voil, and on the hill-slope south of Loch 
Doine, but these are of little structural importance. 
The long stretch of alluvium that separates Loch Voil from Loch 
Lubnaig has been laid down by the Calair burn in Glen Buckie, by the 
Kirkton burn at Balquhidder, and by various streams on both sides of 
Strathyre. The silting up now in progress at the head of Loch Lubnaig 
is well shown by the tongues of alluvium, on both sides of the Balvag 
river, that project for some distance into the loch and isolate small 
basins of fresh water. About half a mile north of Loch Lubnaig a 
moraine rises out of the alluvium, probably a fragment of the adjacent 
moraine on both sides of the valley. As the top of this moraine probably 
rose above the level of the ancient united lake, the depth of the latter 
near this locality could not have been very great. 
A glance at the chart of Loch Lubnaig will show that its floor is 
much more irregular than that of Loch Voil. This may be accounted 
for partly by the presence of alluvial cones formed by various streams, 
and by features connected with the geological structure of the basin. 
The deepest parts of this lake form two basins enclosed by the 
100-feet contour-line, one to the north and the other to the south of 
Ardchullarie More. The upper one, about 500 yards long, is 146 feet 
deep, and the lower one, about 900 yards long, is 108 feet in depth. 
Though now separated by alluvial detritus brought down by the Ard- 
chullarie burn from the north-east, and by the Dubh Shruith burn from 
the south-west, these basins were probably originally continuous. The 
powerful Loch Tay fault with a N.N.E. and S.S.W. course, and with a 
downthrow to the west, crosses Loch Lubnaig immediately to the south 
