THE FEESH-WATER LOCHS OP SCOTLAND. 
205 
THE LOCHS OF LEWIS. 
The island of Lewis and Harris is the largest of the lesser British 
islands (see Index Map, Fig. 23), only Skye and the Mainland of Shetland 
nearly approaching it in size. It measures some 60 miles in length by 
30 miles in breadth. Its southern half is mountainous, many peaks 
exceeding 2000 feet in height, and a few exceeding 2600 feet. The 
northern half is lower. 
There are many hundreds of lochs distributed over every part of the 
island. In the northern half they are specially numerous, and in the 
central part they form a sort of watery maze like that of North Uist. 
There are only a few of the narrow, straight, valley lochs, so familiar 
on the mainland of Scotland, and those are in the southern mountainous 
part of the island ; the majority are small, roundish, or relatively broad, 
and the larger ones of extremely irregular form. It was only possible 
to survey a small in’o^jortion of the numerous lochs, thirty altogether 
being sounded. 
Five of the lochs exceed 2 miles in length. Loch Langavat is by far 
the longest, exceeding 7 miles, and in superficial area is about four times 
as great as any other loch. It is, however, exceeded in volume by Loch 
Suainaval, which contains 2843 millions of cubic feet. Loch Suainaval 
is also by far the deepest loch, exceeding 200 feet in maximum depth, 
while no other loch exceeds 100 feet. Five lochs, Langavat, Scaslavat, 
Grunavat, Benisval, and Raonasgail, approach 100 feet in depth. The 
mean depth of Loch Suainaval is 108 feet, no other loch exceeding 35 
feet. Combining the areas of all the lochs, the extent of fresh water sur- 
veyed amounts to nearly 10 square miles, the volume of water to 7400 
millions of cubic feet. 
The thirty lochs of Lewis surveyed are contained in seventeen distinct 
basins, draining independently into the sea. Twelve of these basins 
contain only one loch which was surveyed ; three contain two lochs ; the 
Thamanabhaidh basin contains four lochs ; the most extensive basin sur- 
veyed is the Laxey basin, with its eight lochs. Many extensive basins 
were not visited at all. 
There follows a table of the seventeen basins and the lochs contained 
in them 
