THE FKESH-WATER LOCHS OF SCOTLAND. 53 



length. The area of the lake-floor covered by less than 25 feet of water 

 is about 39 acres, that covered by water between 25 and 50 feet in depth 

 is about 37 acres, and that covered by more than 50 feet of water is about 

 23 acres. 



Temperature Observations. A series of temperatures taken in the 

 deepest part of the loch at 1.30 p.m. on the date of the survey gave the 

 following results : 



Surface 56-0 Fahr. 



5 feet 55-9 



10 55-9 



20 55-8 



50 55-l 



58 52-2 



65 51'0 



These observations give a total range of temperature of 5*0, the upper 

 layers of water being practically uniform in temperature, while between 

 50 and 65 feet there is a fall amounting to 4r'l. 



Loch Bad an Sgalaig (see Plate XVIII.). Loch Bad an Sgalaig (or 

 Bad-na-Skallaig, or Batnaskalloch) is somewhat egg-shaped, though 

 irregular, in outline (see Fig. 30), with a length from north to south 

 exceeding two-thirds of a mile, and a maximum breadth from east to west 

 of nearly half a mile. Its waters cover an area of about 137 acres, and 

 it drains directly an area of over 7 square miles, but since it receives 

 the overflow from Dubh Loch and Loch na h-Oidche its total drainage 

 area exceeds 12 J square miles. The maximum depth of 64 feet was 

 observed approximately near the middle of the loch, though rather nearer 

 the southern than the northern shore. The volume of water is estimated 

 at 151 million cubic feet, and the mean depth at 24~ feet. The loch was 

 surveyed on July 30, 1 902, when the elevation of the lake-surface above the 

 sea was determined by levelling from bench-mark as being 352*6 feet 

 almost identical with the elevation recorded by the Ordnance Survey 

 officers on July 8, 1870, viz. 352'5 feet above sea-level. Between July 30 

 and August 2, 1902 (when Dnbh Loch was sounded), the water in Loch 

 Bad an Sgalaig rose to the extent of 9 inches. 



Loch Bad an Sgalaig is simple in conformation ; though the contour- 

 lines are somewhat sinuous in character, the cross-lines of soundings indicate 

 a bottom sloping gradually from the shores towards the deep water in the 

 middle. In places the contour-lines approach close to each other or to the 

 shore-line, as, for instance, off the central portion of the western shore, 

 where a sounding in 20 feet was taken about 50 feet from shore, but on the 

 whole the soundings give no indication of any very steep gradients. The 

 following table gives the approximate areas between the contour-lines, and 

 the percentages to the total area of the loch : 



