194 . BATHYMETRICAL SURVEY OF 



under the 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 27J 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 Crogavat. 



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 55-0 Fahr. 



25 feet 55-0 



50 54-5 



70 50-4 



85 49-0 



Loch Crogavat (see Plate LXXVL). Loch Crogavat 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, 24 J feet, is relatively high, being only exceeded by 

 Lochs Obisary andfra' 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' Ghlinue- 

 Dorcha, standing 22'45 feet above sea-level.] 



Loch Obisary (see Plate LXXVL). The largest loch in North Uist, 

 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 lino 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 



