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 Xth, 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 overfiow from Loch 
Affric its total drainage area is about 52| 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 37 J 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 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 15 J 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 
