THE FRESH-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 Ohsermtions . — 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 4°'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 12J 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 24J feet. The loch was 
surveyed on July 30, 1902, 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 
ofiicers on July 8, 1870, viz. 352*5 feet above sea-level. Between July 30 
and August 2, 1902 (when Dubh 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 : — 
