THE FRESH- WATER LOCHS OF SCOTLAND. 93 



the length. Its waters cover an area of about 111 acres, or over one- 

 sixth of a square mile, and it drains an area nearly 30 times greater, 

 or over 5 square miles. Nearly 60 soundings were taken, the maximum 

 depth observed being 95 feet. The volume of water is estimated at 

 189,623,000 cubic feet, and the mean depth at 39 feet, or 41 per cent, 

 of the maximum depth. The length of the loch is 53 times the maximum 

 depth and 130 times the mean depth. The loch is of simple conforma- 

 tion, and, on the whole, comparatively deep, only half a dozen soundings 

 under 10 feet being recorded close to the shore. Off the northern shore, 

 towards the west end, the slope of the bottom is very steep, soundings 

 of 31 feet and 44 feet having been taken about 80 and 100 feet from the 

 shore respectively; this is equal to a slope of 1 in 2-3 to 2-6. The 

 eastern end, and south-eastern portion of the loch around the island, are 

 comparatively shallow. The 25-feet basin is about three-quarters of a 

 mile in length, stretching from quite close to the west end to within 

 one-sixth of a mile from the east end. The 50-feet basin is nearly half 

 a mile in length, and the 75-feet basin, occupying the western half of 

 the loch, is over one-third of a mile in length. The maximum depth 

 of 95 feet was observed in two places approximately near the centre of 

 the wide western portion of the loch. The area of the lake-floor 

 covered by less than 25 feet of water is about 50J acres, or over 45 per 

 cent, of the total area of the loch ; that covered by water between 25 

 and 50 feet in depth is about 21J acres, or over 19 per cent.; that 

 covered by water between 50 and 75 feet in depth is about 19 acres, or 

 17 per cent. ; and that covered by more than 75 feet of water is about 

 20J acres, or over 18 per cent, of the entire area of the loch. The flat- 

 bottomed character of the deep western portion of the loch is well 

 brought out by a comparison of the last two percentages, while the high 

 percentage of the bottom covered by less than 25 feet of water is due to 

 the comparatively large shallow area in the south-eastern and eastern 

 part of the loch. Loch Daimh was surveyed on May 26, 1903, but the 

 level of the surface of the water above the sea could not be determined. 

 Temperature Observations. The temperature of the surface water 

 on commencing the survey at 9.30 a.m. on May 26, 1903, was 51*0 

 Fahr., and a series of temperatures taken in the deepest part of the 

 loch gave the following results : 



Surface 50 -3 Fahr. 



10 feet 47-0 



25 44-0 



50 43'5 



90 ,, 43-0 



The range in the temperature of the water from surface to bottom was 

 thus 7'3. The fall of temperature from the surface to a depth of 

 10 feet amounted to 3-3, and that between the depths of 10 and 25 feet 

 amounted to 3-0, and below 25 feet the fall amounted to 1-0. 



