274 



BATHYMETRICAL SURVEY OF 



narrowing towards the eastern end. It is over If miles in length, with 

 a maximum breadth of one-third of a mile, the mean breadth being a 

 quarter of a mile. Its waters cover an area of 267 acres, or nearly half 

 a square mile, and it drains an area 72 times greater an area exceed- 

 ing 30 square miles. The maximum depth of 176 feet was observed 

 approximately near the centre of the loch. The volume of water is 

 estimated at 819 million cubic feet, and the mean depth at 70 J feet. 

 The loch was surveyed on August 22, 1902, when the elevation of the 

 lake-surface was found to be 465-6 feet above sea-level; when visited 

 by the officers of the Ordnance Survey on June 6, 1870, the elevation 

 was 465' 1 feet above the sea. 



Loch Beannachan forms a simple basin, the contour-lines following 

 approximately the outline of the loch, but approaching in each case 

 nearer to the western than to the eastern end. There is a large wooded 

 island at the entrance of the inflowing river at the west end, and a 

 small island near the exit of the outflowing river at the opposite end. 

 The slope offshore is in some places very steep, especially at certain 

 points along the southern shore, and at the position of the deepest 

 sounding the slope is steeper off the southern than off the northern 

 shore, as is shown in the cross section C-D on the map. The longi- 

 tudinal section A-B shows the gradual slope towards the two ends, 

 with quite a flat-bottomed character in the deeper water, which is also 

 indicated by the larger area between 100 and 150 feet than between 

 50 and 100 feet, as given in the following table: 



to 50 feet 

 50,, 100 

 100 150 

 Over 150 , 



113 acres 

 67 

 72 

 15 



267 



42-3 per cent. 

 25-0 



27 '2 

 5 '5 



100-0 



Temperature Observations. A series of temperatures taken in the 

 deepest part of the loch at 4.15 p.m. on August 22, 1902, gave the 

 following results : 



Surface 



10 feet 



20 



30 



40 



50 



60 



75 

 100 

 170 



55'OFahr. 

 55 -0 

 54 -8 

 53 -0 

 52 -9 

 52 -0 

 50 -5 

 46 -9 

 46 -1 

 46 -0 



