316 
BATHYMETRICAL SURVEY OF 
LOCHS OF THE BORGIE BASIN. 
The three lochs to be dealt with here form a connected series, the 
overflow from Loch Cuil na Sithe being carried into Loch Laoghal by 
the Lon Achadh na h-Aibhne, while Lochs Laoghal and Creagach are 
almost continuous, the connecting stream being only about 200 yards 
in length. Of the total area of the basin (about 62 square miles), about 
35 square miles, or 56 per cent,, drain into these three lochs. 
Loch Chil na Sithe (see Plate LXXIV.). — Loch Cuil na Sithe (or 
Coulside) is a small narrow loch lying over a mile to the west of the head 
of Loch Laoghal, and about 5 miles to the north of Altnaharra, at the 
head of Loch Naver. It trends east-north-east and west-south-west, 
and is very nearly a mile in length, varying little in width, the 
maximum breadth being about 250 yards. Its waters cover an area 
of about 58 acres, and it receives the drainage from a comparatively 
large tract of country, the drainage area being about 9 square miles — 
an area a hundred times greater than that of the loch. The maximum 
depth of 14 feet was observed in two places near the middle of the 
loch. The volume of water is estimated at 19 million cubic feet, and 
the mean depth at feet. The loch was surveyed on September 29, 
1902, but the elevation of the lake-surface above the sea could not be 
determined ; a drift-mark was observed over 6 feet above the water, 
which might fall to the extent of a foot, giving a range in level 
exceeding 7 feet. 
Loch Cuil na Sithe is extremely simple in conformation, and com- 
paratively uniform in depth. The upper portion is being silted up, 
and is occupied by weeds, and the lower portion is full of stones. The 
10-feet contour coincides approximately with the outline of the loch, 
and encloses an area of about 20 acres, or 35 per cent, of the total 
area of the loch. The temperature of the surface water on the date of 
the survey was 56°*2 Fahr., and a reading at a depth of 11 feet gave 
53°*9. 
Loch Laoghal (see Plate LXXV.). — Loch Laoghal (or Loyal) is 
distant about miles from Tongue and about 6 miles from Altnaharra, 
the road between these two places running alongside the western shore 
of the loch throughout its whole length. To the west rises Ben Loyal, 
