THE FRKSH- WATER LOCHS OF SCOTLAND. 267 



than half a degree lower than in the north loch); between 20 and 

 30 feet the fall was l-2, and between 30 and 40 feet l-7 a fall of 

 nearly 3 in the 20 feet of depth. 



Loch Achanalt (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' Chuiliiin 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 

 72J 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 365*1 feet 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 a' 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 1 J 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 1J 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 10J 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 



