THE FRESH- WATER LOCHS OF SCOTLAND. 
169 
The loch was surveyed on April 17 and 18, 1903, when the elevation 
was found to be 702-9 feet above the sea, or a little higher than that 
observed by the Ordnance Survey officers on April 8, 1871, viz. 702*3 feet 
above sea-level. Temperatures taken on April 18 showed that the water 
was practically uniform in temperature throughout, the readings being : — 
Loch a’ Chlachain (see Plate LXIV.) lies immediately to the east of Loch 
Dun na Seilcheig, the difference in level being about 20 feet. The western 
shore consists of moraine mounds, which, where cut through by the road, 
are seen to be composed of yellow gravel, with many immense boulders, 
some perched ; a very large boulder forms a projecting point near the 
northern end of the loch. To the east the whole hillside is strewn with 
large boulders, with perched blocks on the higher hills. 
The loch is irregular in outline, trending nearly north and south, 
and is half a mile in length by one-third of a mile in maximum 
breadth, covering an area of about 60 acres. The drainage area exceeds 
10 square miles, including Lochs Ceo-Glas and Dim na Seilcheig. The 
loch forms a simple basin with an extensive shallow flat at the southern 
end, due, apparently, to the deposition of material by the inflowing stream. 
The deeper water lies towards the central part of the eastern shore, off 
which two soundings at the maximum depth of 80 feet were recorded. The 
volume of water is estimated at 78 million cubic feet, and the mean depth 
at 30 feet, nearly one-half of the lake-floor being covered by less than 25 
feet of water. The loch was surveyed on April 29, 1903, when the eleva- 
tion was found to be 683*7 feet above the sea, or a little higher than that 
observed by the Ordnance Survey officers on April 13, 1871, viz. 683*3 
The temperature of the water from surface to bottom varied little, the 
reading at the surface being 42°*7 Fahr. ; at 10, 25, and 50 feet, 42°*5 ; and 
at 75 feet, 42°*0. 
From the following table it will bo seen that in the ten lochs under 
consideration 655 soundings were taken, and that the aggregate area of the 
water-surface is 3^ square miles, so that the average number of soundings 
per square mile of surface is 187. The aggregate volume of water con- 
tained in the lochs is estimated at 5179 millions of cubic feet. The area 
drained by these lochs is nearly 42J square miles, or about twelve times 
the area of the lochs. 
Surface . 
100 feet . 
190 „ . 
39°-5 Fahr. 
39°-4 
39°-2 „ 
feet. 
