THE FRESH- WATER LOCHS OF SCOTLAND. 119 



soundings taken giving a depth of 9 feet. The shores are mostly of rock, 

 with stony debris, sandy gravel covering the eastern shore at the narrow 

 part near the north end. The temperature of the surface water on the 

 date of the survey varied from 58" -5 to 60- 5 Fahr., a reading at a depth 

 of 8 feet giving 58-0. 



Loch Ken (see Plate XLV.). Loch Ken is the largest in the basin, 

 trending from north-west to south-east, the northern end being over a mile 

 south of New Galloway, and the southern end about 7 miles north of Castle 

 Douglas, the confluence of the Black Water of Dee with the river Dee being 

 looked upon as the southern limit of Loch Ken. The length exceeds 4J miles, 

 the maximum breadth across the centre of the loch at the entrance of the 

 Dullarg burn being about half a mile, and the mean breadth over a quarter 

 of a mile. The waters of the loch cover an area of about 867 acres, or 1^ 

 square miles, and the area draining into it is very large, extending far to 

 the north and west, and including the other lochs within the basin dealt 

 with in the preceding pages, as well as a few lochs which were not 

 surveyed. The total drainage area thus amounts to about 282 square 

 miles. The maximum depth of 62 feet was recorded about a mile from the 

 upper end. The- volume of water is estimated at 792 millions of cubic 

 feet, and the mean depth at 21 feet. The loch was surveyed on July 

 14, 1903, the elevation being 142-0 feet above the sea. 



The floor of Loch Ken is irregular, there being six separated areas 

 where the depth exceeds 25 feet, and two areas where the depth exceeds 

 50 feet. The 20-feet contour would be continuous almost from end to end, 

 except for a slight break opposite the entrance of the Arvie burn, where 

 the deepest sounding was 19 feet. The deepest basin occupies the wide 

 portion at the head of the loch, where there is a 25-feet area over 1 J miles 

 in length, enclosing a 50-feet area over three-quarters of a mile in length, 

 the maximum depth of 62 feet having been observed towards the eastern 

 shore. The second 50-feet area, based on a sounding in 52 feet, lies less 

 than a mile from the foot of the loch, occupying a central position in a 

 25-feet area three-quarters of a mile in length. To the south of this area 

 the water deepens again to 31 feet, and near the entrance of the Black 

 Water of Dee another sounding in 33 feet was taken. Of the entire lake- 

 floor 7 1 per cent, is covered by less than 25 fee* of water. 



Temperature Observations. Serial temperatures taken in the deepest 

 basin showed a gradual decrease of temperature, the total range from 

 surface to bottom being 4-7 Fahr., as follows : 



Surface 60-2 Fahr. 



25 feet 59-5 



30 58-5 



35 57-5 



40 -... 56-5 



55 55-5 



Expansions of the River Dee (see Plate XLV.J. The expansions of the 



