THE FRESH- WATER LOCHS OF SCOTLAND. 61 



(2968 feet) rising to the north-west, and Creag a' Chaoruinn Eagan 

 (22(30 feet) to the south. On its south side the shore of the loch rises 

 steeply to the ridge of Creag an Eilein, the highest part of which 

 (1137 feet) is about a quarter of a mile distant. The loch trends north- 

 east and south-west, and is 2 miles in length, with a maximum breadth 

 of less than half a mile near the north-east end, whence it tapers oflf 

 towards the south-west, the lower end for half a mile being merely a series 

 of small expansions of the river Carron. Its waters cover an area of about 

 283 acres, and it drains directly an area of 3l| square miles, but since it 

 receives the overflow from Loch Sgamhain the total drainage area is 39 

 square miles. The maximum depth of 179 feet was observed opposite the 

 highest part of Creag an Eilein, less than half a mile from the north-east 

 end. The volume of water is estimated at 823 million cubic feet, and the 

 mean depth at nearly 67 feet. The loch was surveyed on August 6 and 7, 

 1902, when the elevation was found to be 93*1 feet above the sea. 



The main body of the loch is simple in conformation, the contour-lines 

 following approximately the shore-line, but there are two 100-feet basins, 

 the main basin being over three-quarters of a mile in length, and approach- 

 ing very close to the north-east end, soundings in 108 and 111 feet having 

 been taken about 120 yards from shore; the smaller basin is based on a 

 single sounding in 105 feet, and is separated from the main basin by a 

 slight shoaling, covered by 97 feet of water, north of Eilean Mor. There 

 are two small basins over 25 feet in depth in the river-expansions at the 

 south-western end of the loch, the larger having a maximum depth of 

 32 feet, the smaller based on a sounding in 28 feet. 



Temperature Observations. A series of temperatures taken in the 

 deepest part of the loch at 4.30 p.m. on August 7, 1902, gave the following 

 results : 



Surface 54-5 Fahr. 



25 feet 54-5 



50 54-0 



60 53-5 



70 50-0 



75 49-3 



100 47-5 



165 47'0 



These observations show a range from surface to bottom of 7^, a fall 

 of 3J being recorded between 60 and 70 feet, while the decrease in 

 temperature both above and below the " sprungschicht " is gradual. 



From the following table it will be seen that in the twelve lochs under 

 consideration nearly 1100 soundings were taken, and that the aggregate 

 area of the water surface is nearly 4 square miles, so that the average 

 number of soundings per square mile is 281. The aggregate volume of 

 water contained in the lochs is estimated at 4921 millions of cubic feet. 

 The area drained by these lochs is nearly 98i square miles, or 25 times 

 the area of the lochs. 



