340 BATHYMETRICAL SURVEY OF 



of water is about 178 acres, as compared with 270 acres covered by 

 water between 50 and 100 feet in depth, or 35 per cent, as compared 

 with 53 per cent. In most lakes the arrangement is the reverse of this, 

 the areas between consecutive contour-lines drawn at equal intervals 

 usually decreasing with increase of depth. The temperature of the 

 surface water at the east end on commencing the survey was 50'0 

 Fahr., while later in the afternoon, towards the opposite end the 

 surface temperature was 49-5 ; but an easterly gale having sprung 

 up, it was found impossible to take serial temperatures beneath the 

 surface. 



Loch na Beinne Baine (see Plate LXXXIL). Loch na Beinne 

 Baine lies in Guisachan forest, about 4 miles to the south-east of Loch 

 Beinn a' Mheadhoin, and 8 or 9 miles to the west of Invermoriston on 

 Loch Ness. It is irregular in outline, trends in a north-north-east and 

 south-south-westerly direction, and is nearly a mile in length, with a 

 maximum breadth of nearly half a mile. The superficial area is about 

 154 acres, or a quarter of a square mile, and the area draining into it 

 about 1J square miles. The maximum depth of 67 feet was observed 

 about a quarter of a mile from the southern end of the loch, midway 

 between an island of stones and the eastern shore. The volume of 

 water is estimated at 190 million cubic feet, and the mean depth at 

 28 J feet. The loch was surveyed on June 6, 1904, but the elevation of 

 the lake-surface above the sea could not be determined ; the height of 

 the water at the sluice was about 2 feet, and at one time the loch 

 appears to have been considerably higher. 



Loch na Beinne Baine forms a simple basin ; the 25-feet contour 

 coincides approximately with the outline of the loch, but is deflected at 

 the position of the island of stones off the western shore towards the 

 southern end, while the 50-feet basin, based on soundings of 67, 64, 54, 

 and 52 feet, is contained in the southern half of the loch, and is about 

 a quarter of a mile in length. The soundings indicate in one or two 

 places slight undulations of the lake-floor, but as a rule the slope of 

 the bottom is regular and gentle. The area covered by less than 25 feet 

 of water is about 95 acres, or 62 per cent, of the total area. 



Temperature Observations. A series of temperatures taken in the 

 deepest part of the loch gave the following results : 



Surface 60 '8 Fahr. 



10 feet 60'0 ,, 



20 50-5 



40 47'6 



60 ... 46'5 



These observations indicate an extreme range of temperature from 

 surface to bottom amounting to 14-3, there being a fall of 9'5 between 



