338 BATHYMETRICAL SURVEY OF 



Loch an Laghair (see Plate LXXIX.). Loch an Laghair lies a 

 little over a mile to the north-east of Loch Affric, and is practically 

 continuous with Loch Beinn a' Mheadhoin, for normally the two lochs 

 stand at the same level, although an easterly gale sets up a strong 

 current through the narrows at Blar an Ath, in which a depth of 

 5 feet was observed. The loch trends in a north-east and south-west 

 direction, and is nearly two-thirds of a mile in length. The maximum 

 width exceeds a quarter of a mile towards the western end, whence 

 the loch narrows gradually towards the eastern end. The superficial 

 area of the loch is about 83 acres, and the area draining directly into it 

 nearly 6 square miles, but since it receives the overflow from Loch 

 Affric its total drainage area is about 52J square miles, an area over 

 400 times greater than that of the loch. The deepest sounding in 100 

 feet was taken in the central part of the loch, but rather nearer to the 

 north-east end. The volume of water is estimated at 135 million cubic 

 feet, and the mean depth at 37J feet. The loch was surveyed on 

 October 6, 1903; but the elevation of the lake-surface above the sea 

 could not be determined by levelling, as there was no bench-mark near 

 the loch. The level was estimated at about 703 feet above sea-level. 



Loch an Laghair forms a simple basin, the shallower contours 

 coinciding approximately with the outline of the loch, but approaching 

 closer to the northern shore in the eastern half of the loch, where the 

 offshore slope is steepest. The western end is apparently being silted 

 up. The 75-feet area is extremely small, for on each side of the 

 deepest sounding in 100 feet, at a distance represented by twenty 

 strokes of the oar, the depths were 66 and 64 feet respectively. A 

 section across the loch at the position of the deepest sounding is shown 

 in cross-section E-F on the map, and a section along both Loch an 

 Laghair and Loch Beinn a' Mheadhoin is shown in the longitudinal 

 section A-B. The area of the lake-floor in Loch an Laghair covered 

 by less than 50 feet of water is about 63 acres, or 76 per cent, of the 

 total area of the loch. The temperature of the surface water at 

 3.30 p.m. on the date of the survey was 48'0 Fahr. 



Loch Beinn a' Mheadhoin (see Plate LXXIX.). Loch Beinn a' 

 Mheadhoin (or Beinnavian, or Beneveian) trends generally in a north- 

 east and south-westerly direction, and is over 2J miles in length. The 

 loch is fairly uniform in width, the two end portions being somewhat 

 narrower than the central portion, which has a maximum breadth of 

 nearly half a mile, the mean breadth of the entire loch exceeding a 

 quarter of a mile. The superficial area of the loch is about 504 acres, 

 or over three-quarters of a square mile, and the area of land draining 

 directly into it is about 15J square miles; but since it receives the 

 superfluent waters from Lochs Affric and an Laghair, the total drainage 

 area is about 68 square miles. The maximum depth of 167 feet was 



