THE FRESH-WATER LOCHS OF SCOTLAND. 
267 
than half a degree lower than in the north loch) ; between 20 and 
30 feet the fall was 1°*2, and between 30 and 40 feet 1°*7 — a fall of 
nearly 3° in the 20 feet of depth. 
Loch Achaiialt (see Plate LVIII.). — Loch Achanalt is an irregular 
shallow loch apparently in process of being silted up, the material 
brought down by the river Bran forming two long spits extending out 
towards the centre of the loch. The northern spit extends nearly across 
the loch, joining the islands, and leaving only a narrow passage close to 
the eastern shore, through which there was a strong current, and thus 
practically cutting the loch into two portions. The western shores 
are bordered by weeds. It flows into Loch a’ Chuilinn by a short and 
rapid stream, the difference in level exceeding 4 feet; the Highland 
railway is carried over the passage between the two lochs. Loch 
Achanalt is approximately quadrangular in outline, its maximum 
diameter exceeding three-quarters of a mile, and it covers an area 
of about 160 acres, or one-quarter of a square mile. The deepest water 
was found comparatively close to the western shore, south of the 
entrance of the river Bran, where two soundings of 9 feet and two 
soundings of 8 feet were recorded. The volume of water is estimated 
at 31 million cubic feet, and the mean depth at 4J feet — half the 
maximum depth. The area draining directly ’ into Loch Achanalt is 
very large, exceeding 39 square miles ; but, since it receives the outflow 
from Lochs a’ Chroisg and Gown, its total drainage area exceeds 
72 J square miles, or 290 times the area of the loch. Loch Achanalt 
was surveyed on August 9, 1902, when the elevation of the lake- 
surface was found to be 365T f.eet above the sea; when levelled by 
the Ordnance Survey officers on May 9, 1870, the elevation was 364-7 
feet above sea-level. The temperature of the surface water on the date 
of the survey was 57°-l Fahr. ; the temperature of the river Bran being 
55°-2. On August 19, 1901, Mr. Clark observed a temperature of 60°’l 
at the surface, and a temperature of 60°-4 at a depth of 5 feet. 
Loch o’ Chuilinn (see Plate LVIII.). — Loch a’ Chuilinn (or Culen) 
trends east and west, is irregular in outline, of varying width, and with 
an undulating floor. It is IJ miles in length, with a maximum breadth 
of one-third of a mile. Its waters cover an area of about 113 acres, and 
it drains directly an area of nearly 1| square miles; but as it receives 
the outflow from Loch Achanalt, its total drainage area is over 74 
square miles — over 400 times the area of the loch. The maximum 
depth of 43 feet was observed approximately near the middle of the 
loch. The volume of water is estimated at 50 million cubic feet and 
the mean depth at lOJ feet. The bottom of Loch a’ Chuilinn is most 
irregular; close to the west end is a 10-feet basin, with a maximum 
depth of 29 feet, the slopes of which are in places steep, depths of 20 
