64 BATHYMETRICAL SURVEY OF 
in the district, or perhaps in Scotland. It is about 5J miles in length 
from north-east to south-west, but it sends out an arm towards the 
west, which is over 1|- miles in length, and a line following the axis of 
the loch from the north-east end to the extremity of the western arm^ 
would be over 6 miles in length. Its maximum breadth is nearly 
three-quarters of a mile, and the mean breadth about one-third of a 
mile, or 6-4 per cent, of the length. Its waters cover an area of about 
1149 acres, or over 1| square miles, and it drains directly an area of 
30J square miles; but, since it receives the outflow from Lochs Ba, 
Achlaise, Stainge, and Buidhe, its total drainage area is over 47 J square 
miles or 26 J times the area of the loch. Nearly 500 soundings were 
taken in the loch, and the maximum depth observed was 128 feet, the 
mean depth being 35 feet, or 27J per cent, of the maximum depth. The 
length of the loch is 219 times the maximum depth, and 795 times the 
mean depth. The volume of water contained in the loch is estimated at 
1,761,733,000 cubic feet. The western extension and the southern end 
of Loch Laidon are filled with boulders and islets, and are like Loch Ba 
in character, but the main basin is of comparatively simple form, 
though with minor undulations of the lake-floor, the deepest water 
occupying the centre of the loch, where there is a basin three-quarters 
of a mile in length and over 100 feet in depth, the maximum depth of 
128 feet having been observed about 2| miles from the south-west end 
and 2J miles from the north-east end. Separated from this main 
100-feet basin by shallower water, there is a sounding of 104 feet a short 
distance to the south-west, and half a mile further south there is an 
isolated sounding of 100 feet; there is also an isolated sounding of 100 
feet a quarter of a mile to the north-east of the main basin. The 
principal 50-feet basin extends from less than a mile from the south- 
west end to less than miles from the north-east end, and is nearly 
3 miles in length. Separated from this larger basin by an interval of 
a quarter of a mile is a smaller one, about one-third of a mile in length, 
situated in the north-eastern part of the loch, and nearly midway 
between them is an isolated sounding of 50 feet. The western arm of 
Loch Laidon is shallow and filled with rocks and boulders, the greatest 
depth observed being 17 feet in three different places. Of the entire 
lake floor, 53 per cent, is covered by less than 25 feet of water, 21 per 
cent, is covered by water between 25 and 50 feet in depth, 22 per cent, 
by water between 50 and 100 feet in depth, and 4 per cent, by water 
exceeding 100 feet in depth. Loch Laidon was surveyed on April 9 to 
25, 1902, and the surface of the loch was found by levelling to be 923*9 
feet above sea-level. When surveyed by the Ordnance Survey officers 
on July 28, 1860, the level of the loch was 924*6 feet above the sea. 
At the north-eastern end of Loch Laidon is a small basin called Dubh 
Lochan, which was found by levelling on April 14, 1902, to be 2 feet 
higher than Loch Laidon, and should therefore, strictly speaking, be 
