214 
BATHYMETKICAL SUEYEY OF 
volume of water 2388 millions of cubic feet. It is the only loch in Lewis 
the area of wbicb exceeds a square mile. Though four times the area of Loch 
Suainaval, the next to it in size, the volume is less by 450 millions of cubic 
feet. The drainage area measures nearly 28 square miles. The feeders 
are all small local streams, the largest, Glen Langadale, at the upper end 
of the loch. From near the northern extremity of the loch two wide 
channels lead into Loch Airidh na h’Airde, whence a chain of lochs, with 
only very short connecting streams, extends some 4 miles northward to the 
head of Loch Roag near Callernish. Locb Coirigerod, Ij miles long, 
which stands at a higher level than Locb Langavat, was not surveyed. 
The surface at the time of the survey (July 13 to 18, 1903) was 
108*0 feet above sea-level. 
Temperature Observations . — The following serials were taken during 
the survey 
Surface 
July 16. 
56°-8 
July 17. 
56°*1 
20 feet 
56°-2 
56°*1 
50 „ 
55°*4 
56°-0 
87 „ 
— 
55°*1 
92 „ 
55°*0 ... 
— 
Loch Grunavat (see Plate LXXXVI.) is a fairly large loch, lying about 
2 miles to the west of Little Loch Eoag. Though of the narrow form of 
valley lochs, it does not occupy a well-marked valley. High land ’occurs at 
the ends of the loch, while the sides are comparatively low. The length 
is 2\ miles, and the greatest breadth, about the middle of the loch, half a 
mile. The shore-line is irregular, with several promontories and deep 
inlets. A large island occupies almost the exact centre of the loch, South 
of the island the loch is almost everywhere shallow ; north of it is a simple 
and comparatively deep basin. The 25-feet and 50-feet contours extend a 
short distance south of the island, the deep channel passing between the 
island and the west shore. Halfway between the island and* the north end 
is a small area over 75 feet in depth, with the maximum of 90 feet. The 
mean depth is 28 feet, the area about 387 acres, and the volume of water 478 
millions of cubic feet. The area draining into the loch is 3 square miles ; 
there are no inflowing streams of any size. The outflow, near the southern 
end of the loch, through the inlet called Loch na Ciste, which could not be 
entered, is by the Gisla river, flowing 2 miles eastward into Little Loch 
Eoag. The surface was 365*4 feet above sea-level on July 28, 1903. 
The temperature had a range of 6° Fahr. from surface to bottom, the 
readings being : — 
Surface 61°*5 Fahr, 
15 feet ... 59°-2 „ 
25 „ 58°*0 „ 
50 „ ... 56°*1 „ 
80 „ 55°-6 „ 
