178 
BATHYMETRICAL SURVEY OF 
casual inspection satisfies us that they can be of no great depth. The 
selection of the lochs to be surveyed was determined by the presence of 
boats, which were found only on some half-dozen of the larger lochs. 
Loch Eeouravay (see Plate LXVIII.j. — Loch Heouravay is a loch of 
extremely irregular form, lying close to the sea-shore on the east side of 
the island, where Loch Uskavagh cuts so deeply into the interior of the 
land. It drains into Heouravay bay, an inlet from Loch Uskavagh, by a 
stream a few yards in length. We were told that there was formerly a 
mill on this stream and that the surface of the loch was kept at a higher 
level by a dam with a sluice. When that was the case Loch Heouravay 
might be a single loch ; the removal of the dam has divided it into five 
distinct little lochs, differing slightly in level, and connected by very short 
streams which fall only a few inches. The surroundings are rough moor- 
land, the shores of rock, overlain in places by gravel and boulders. There 
is rock close by the outflow. 
The length, in a straight line between the most distant points, is 1| 
miles, following the middle line of the loch If miles. The greatest 
breadth is a quarter of a mile, the mean breadth one-twelfth of a mile. The 
greatest depth in the largest western basin of the loch is 25 feet ; the 
maximum for the whole loch is in the smaller second basin, south of the 
first, where there is a depth of 41 feet close to the shore ; the third basin, 
south of the second, has a depth of 1 0 feet ; and the fourth and fifth 
basins are only 5 and G feet deep. The mean depth of the whole loch is 
about 7 feet. The superficial area is about 80 acres, and the contents 26 
millions of cubic feet. The drainage area is nearly 2 square miles, and 
includes many small lochs. 
The surface of the lowest basin was 8’3 feet above sea-level, the upper- 
most basin 9*6, and the largest fall, between first and second basins, 9 
inches. The temperatures in the deepest basin on June 29, 1904, were — 
Surface . 
15 feet . 
25 „ . 
60°-0 Fahr. 
59°-0 „ 
56°-6 „ 
55°-6 „ 
Loch nan Auscot (see Plate LXVIII.).— -Loch nan Aiiscot is a very small, 
roughly triangular loch, situated between Loch Pleouravay and Loch 
Hermidale. Its long axis runs north and south ; it is broadest towards the 
south and narrows northwards to a point near Loch Hermidale into which 
it drains by a very short stream. The shores are entirely of rock. It is 
a quarter of a mile long, one-tenth of a mile in greatest breadth, and one- 
twentieth of a . mile in mean breadth. Eelatively it is the deepest loch 
surveyed in Benbecula, the maximum depth being 39 feet, and the mean 
depth 17 feet. The area of the surface is only about 8 acres, and it 
receives only surface drainage. The surface level was 13*0 feet above the sea. 
The basin is quite simple, with deep water (of over 35 feet) in a straight 
