THE FRESH- WATER LOCHS OF SCOTLAND. 303 



occupies a central position. The offshore slope is in some places very 

 steep, and the average slope outside the 25-feet contour is steeper 

 than in the deeper water between 25 and 50 feet, as shown in the 

 following table giving the areas between the contour-lines, and the 

 percentages to the total area of the loch : 



to 25 feet 77 acres 44 '5 per cent. 



25 50 87 50-6 



Over 50 , 9 . 4 -9 



173 100-0 



The surface temperature on August 23, 1902, at 12.30 p.m., was 

 57 Fahr.; and on August 25, at 11.45 a.m., 56. 



Loch Migdale (see Plate LXX.). Loch Migdale is situated close to 

 the northern shore of the Dornoch firth, and less than a mile from Bonar 

 Bridge at the head of that firth. It contains trout and pike, and the 

 surrounding scenery is very fine, a conspicuous hill called Migdale Rock 

 rising off the north-eastern shore. The island at the west end of the 

 loch is artificial, composed of large and small stones ; a crossing passes 

 from the western shore to the island, and was covered by a foot of water 

 at the time of the survey. The loch trends in a north-west and south- 

 east direction, and is nearly 2 miles in length, with a maximum width 

 of nearly half a mile towards the north-west end, the loch narrowing 

 gradually towards the opposite end. Its waters cover an area of 

 about 260 acres, and it drains an area of about 7J square miles. The 

 maximum depth of 49 feet was observed rather nearer the north-west 

 than the south-east end. The volume of water is estimated at 242 

 million cubic feet, and the mean depth at over 21 feet. Loch Migdale 

 was surveyed on September 24, 1902, when the elevation of the lake- 

 surface was found to be 113-6 feet above the sea; when visited by the 

 Ordnance Survey officers on November 1, 1869, the elevation was 115'1 

 feet above sea-level. 



The loch forms a simple basin, with a few minor undulations of 

 the lake-floor. The contour-lines approach nearer to the eastern end, 

 where the Spinningdale burn flows out, the water being shallower 

 towards the opposite end, with weeds growing off the northern shore, 

 at the entrances of Migdale burn and Munroe's burn. The area of the 

 lake-floor covered by less than 10 feet of water is about 70 acres, or 

 27 per cent, of the total area, while that covered by more than 25 feet 

 of water is about 94 acres, or 36 per cent. Temperatures taken at 

 6 p.m. on the date of the survey, in the deepest part of the loch, 

 showed very little variation in the temperature of the water, the reading 

 at the surface being 54-9 Fahr., at 25 feet 54'l, and at 40 feet 54. 



