194 
BATHYMETRICAL SURVEY OF j | 
under tlie cliffs on the north, where there is a depth of 36 feet. The 
southern half is a simple basin, free from islands, with fairly steep slopes 
on all sides, and a maximum depth of 85 feet in the centre. The mean 
depth of over 27 J feet is the greatest in the Uist lochs. The shore is 
entirely steep and rocky, forming cliffs under Burrival, and on the north 
a burn a few yards in length leads to Loch Orogavat. 
The surface on June 25, 1904, was 23*2 feet above sea-level. There 
was a difference of 6° between the temperature at the surface and at the 
bottom " 
Surface 
25 feet 
50 „ 
70 „ 
85 „ 
Loch Crogavat (see Plate LXXVl.). — Loch Orogavat lies to the south 
of Loch Eport, near its mouth. It approaches at both ends within a few 
yards of Loch Eport, but it drains eastward into the Little Minch. It 
is over a mile long, by a quarter of a mile broad, and covers an area of 
about 84 acres. In general form it is dumb-bell shaped, narrow in the 
middle and expanded at each end. In the western half is a large island. 
There is deep water on both sides of this island, depths of 40 feet occur- 
ring in the narrow channel to the north of it, as well as in the broader 
part on the south. The eastern basin is larger, of oblong form, with 
many small islands. The maximum depth is 55 feet. The channel 
connecting the two basins is also deep, ranging from 37 feet to 45 feet. 
The mean depth, 24J feet, is relatively high, being only exceeded by 
Lochs Obisary and a’ Ghlinne-Dorcha. The shores and islands are 
entirely of rock. The temperature on June 25, 1904, was uniform 
throughout, viz. 55°*2 Fahr. at the surface, and at the depths of 25 and 
50 feet. Loch Crogavat is less than a foot lower than Loch a’ Ghlinne- 
Dorcha, standing 22'45 feet above seadevel.] 
Loch Ohisary (see Plate LXXYL).' — The largest loch in North TJist, 
measured by the volume of water, which amounts to 837 millions of cubic 
feet, or twice that of Loch Scadavay. It is also by far the deepest loch 
on the island, the maximum depth of 151 feet being nearly twice that 
of Loch a’ Ghlinne-Dorcha, the second deepest. Loch Scadavay, however, 
is longer, and has a greater superficial area. 
Loch Obisary lies at the foot of Eaval, the highest hill in North Uist 
(1138 feet), which it half encircles, its shores following the curve of the 
mountain on the north and west. It is roughly crescent- shaped, and 
measures 2| miles in a straight line between the points of the crescent, 
or over 3 miles following the axis of maximum depth. It is broadest 
in the northern part, where it measures over one mile across. There are, 
however, large islands in this part of the loch, so that the broadest open 
55“-0 „ 
54°-5 „ 
50°-4 „ 
49°-0 .. 
