316 BATHYMETRICAL SURVEY OF 



LOCHS OF THE BOUGIE 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 Lbn 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 Cbil 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 7J 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 4| 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, 



