THE FRESH- WATER LOCHS OF SCOTLAND. 157 
southern shore. The areas between the consecutive contour-lines, and 
the percentages to the total area of the loch, are as follows; — 
0 to 25 feet 
•25 „ 50 „ 
Over 50 ,, 
109 acres 
45 „ 
6 „ 
160 ,, 
68 ’3 per cent. 
28-0 
100-0 
Loch Crocach was surveyed on September 17, 1902, but the elevation 
of the lake-surface above the sea could not be determined ; the elevation 
must be between 350 and 370 feet above sea-level. The boatman stated 
that the water might rise 2 feet above, and fall 3 feet below, the level 
on the date of the survey. 
Temperature Observations. — Temperature observations showed a 
greater variation than was observed in the larger and deeper Loch 
Assynt, as will be seen from the following serial taken at 2.30 p.m. on 
September 17, 1902 : — 
Surface ... .. ... ... .. ... .. 53°*7 Fahr. 
' 40 feet 53° 2 „ 
70 „ 50°-8 ,, 
This series shows a range of 3°, the greatest fall of temperature 
occurring in deep water below 40 feet. 
Loch an Tuirc (see Plate XXXVII.). — Loch an Tuirc is situated 
about two miles north-east of Loch Inver, and over a mile to the west 
of Loch Beannach. It receives the outflow from Loch Crocach, and 
flows by the Uidh nan Caorach into Loch an Aite Mhbir, thence 
through three other small lochs into Loch Boe. The ground around the 
loch is low, the greatest elevation being one of 400 feet to the north-west 
of the loch. Islands are not so numerous in this loch as in the neigh- 
bouring Lochs Beannach and Crocach ; weeds are very abundant in 
some parts of the loch. Loch an Tuirc trends north-east and south- 
west, and is irregular in outline and conformation. There is a con- 
striction near the centre of the loch, which cuts the deeper water into 
two portions, and the loch narrows gradually towards the outflow at the 
south-west end. It is about four-fifths of a mile (or about 1400 yards) 
in length, with a maximum breadth of one-fifth of a mile (or over 300 
yards), the mean breadth being one-tenth of a mile. Its waters cover 
an area of about 53 acres, and it drains directly an area of about 
square miles, but, since it receives the outflow from Loch Crocach, its 
total drainage area is nearly 3 square miles. Nearly 100 soundings 
were taken, the maximum depth observed being 39 feet. The volume of 
water is estimated at about 24,787,000 cubic feet, and the mean depth 
at lOJ feet. The portion of the loch to the north-east of the central 
