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 lj 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 10 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 0^ 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 the 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 C *5 Fahr. 



Loch Achall (see Plate XV.). Loch Achall (or Achallt) lies about 

 2 miles east of Ullapool, in Glen Achall, through which the Rhidorroch 

 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 1J 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. 



