THE FRESH-WATER LOCHS OF SCOTLAND. 
39 
trends in an east and west direction, with a slight bend near the middle, 
so that the eastern portion dips south-east, and is Ij miles in length, with 
a maximum breadth of a quarter of a mile. The superficial area is about 
116 acres, and the drainage area about 3 square miles. The maximum 
depth of 16 feet was observed about 300 yards from the north-eastern 
shore, towards the east end of the loch. The volume is estimated at 
32 million cubic feet, and the mean depth at 6| feet. 
The loch was surveyed on August 20, 1902, when the elevation was 
found to be 884*1 feet above the sea ; the water could rise only about a 
foot higher. The loch is mostly artificial, only a small portion towards 
the east end having existed previous to the building of the embankment 
at what is now the west end of the loch. This agrees with thq evidence 
of the levelling, for from observations it was determined that the water 
was 11 feet higher than it would be without the embankment, so that a 
contour-line drawn in at 11 feet would enclose the original loch. Of 
the total area of the present lake-floor, about 84 per cent, is covered by 
less than 10 feet of water. The surface temperature on the date of the 
survey was 56°*5 Fahr. 
Loch Achall (see Plate XV.). — Loch Achall (or Achallt) lies about 
2 miles east of Ullapool, in Glen Achall, through which the Khidorroch 
river flows, the shores of both river and loch being, for the most part, 
well wooded. The loch is irregular in outline, and trends in an east and 
west direction. The length exceeds If miles, the maximum breadth being 
nearly half a mile, and the mean breadth over a quarter of a mile. The 
superficial area is about 330 acres, or half a square mile, and the drainage 
area about 29 square miles. The maximum depth of 70 feet was recorded 
near the centre of the loch, but towards the north shore and the west end. 
The volume of water is estimated at 401 million cubic feet, and the mean 
depth at 28 feet. 
The loch was surveyed on August 23, 1902, when the elevation was 
found to be 263*4 feet above the sea, or 1^ feet lower than that observed 
by the Ordnance Survey officers on July 23, 1870, viz. 264*9 feet. The 
boatman stated that the water might fall half a foot lower than the level 
on the date of the survey, while during the preceding winter it had risen 
4J feet above that level, so that the range in level is about 5 feet. The 
lake-floor is irregular, the 25-feet area being almost cut into two portions 
near the west end, where shallow water runs out from the northern shore 
considerably beyond the centre of the loch. The 50-feet area is over 
half a mile in length, and approaches close to the shallow water above 
mentioned, a distance of less than 250 yards separating a sounding in 
55 feet from one in 18 feet. 
The temperature of the surface-water on the date of the survey was 
56°*0 Fahr. 
