42 BATHYMETRICAL SURVEY OF 



This series shows a total range of temperature amounting to about 7, 

 the greatest fall observed being one of about 3 between 75 and 100 feet. 



Fionn Loch (see Plate XVII.). The Fionn Loch, a large irregular 

 sheet of water, lies less than 3 miles to the north-east of Loch Maree. 

 It is a good trout loch, and contains also Salmo ferox, but the fishing 

 is strictly preserved. The lower portion does not lie in a well-marked glen, 

 though round the upper end rise some precipitous and high mountains. 

 There are many large islands, and almost everywhere around the shores, 

 and in places at some considerable distance from shore, large rocks and 

 boulders rise above the surface of the water. The head of the Fionn 

 Loch is practically continuous with the Dubh Loch, which are separated 

 from each other only by an artificial causeway built on a sandbank. When 

 the water is high this causeway is flooded, though under ordinary circum- 

 stances the difference of level is about a foot. The matter was the subject 

 of litigation in 1877, the Lord Ordinary deciding that the lochs were one, 

 but the House of Lords reversed this decision. In this place the two 

 lochs are treated separately. 



The general trend of the Fionn Loch is from south-east to north-west, 

 its total length being 5f miles ; it varies greatly in width, the maximum 

 breadth being about Ij miles, the mean breadth of the entire loch being 

 nearly two-thirds of a mile. Its waters cover an area of about 2250 acres, 

 or over 3J square miles, and it drains directly an area of nearly 15 square 

 miles, but since it receives the outflow from the Dubh Loch, Lochan 

 Beannach, and Loch na Moine Buige, its total drainage area is about 26J 

 square miles. The maximum depth of 144 feet was observed in two 

 places: (1) near the south-eastern end, and (2) in the central part of 

 the loch opposite the entrance of the stream bearing the outflow from 

 Lochan Beannach. The volume of water contained in the loch is 

 estimated at 5667 millions of cubic feet, and the mean depth at 57-f feet. 



The Fionn Loch was surveyed on August 4 to 8, 1902, but the elevation 

 of the lake-surface could not be determined by levelling, owing to the 

 inability of the surveyors to find bench-marks after prolonged search ; 

 when visited by the Ordnance Survey officers on September 2, 1870, the 

 elevation was found to be 558'6 feet above the sea. The keeper stated 

 that the water may rise 5 feet and fall about 2 feet from the level on 

 the date of the survey. The bottom of the Fionn Loch is most irregular, 

 and the contour-lines in most places extremely sinuous in character ; the 

 north-western end is filled with boulders, which often rise out of com- 

 paratively deep water in an astonishing manner. The main 50-feet basin 

 is nearly 4 miles in length, approaching quite close to the south-eastern 

 end, and extending between the islands called Eilean Fraoch and Eilean 

 nan Corr-scriach. A second 50-feet basin runs in a north and south 

 direction, along the centre of the large arm thrown out in a northerly 

 direction towards the foot of the loch, extending to the west of Eilean nan 



