52 
BATHYMETRICAL SURVEY OF 
lines drawn in at equal intervals, and the percentages to the total area, 
for it will be observed that the area between the 25-feet and 50-feet 
contours is smaller than in the deej)er zones, while the area of the lake>^ 
floor covered by more than 100 feet of water is very considerable : — 
Feet. 
Acres. 
Per cent. 
0 to 25 
107 
30-9 
25 „ 50 
59 
17-0 
50 „ 75 
70 
20-1 
75 „ 100 
63 
18-3 
Over 100 
48 
13-7 
- 
347 
100-0 
Temperature Observations . — A series of temperatures taken in the 
deepest part of the loch at 
following results : — 
5 p.m. on the date of the survey 
Surface ... 
51°-0 Fahr. 
20 feet ... 
51°-0 „ 
50 „ ... 
50"’-5 „ 
80 „ ... 
17°-2 „ 
100 „ ... 
46°-8 „ 
These observations give a total range of temperature throughout the 
body of water of 4°*2, the “ sj^rungschicht ” occurring between 50 and 
80 feet, where a fall of 3°-3 was recorded. 
Dubli Loch (see Plate XYIII.). — Dubh Loch lies about 3 miles to the 
south-east of Loch GaiiToch, and is almost continuous with Loch Bad an 
Sgalaig, the stream between them being about 300 yards in length, and 
the diiference in level about 4 feet. The loch trends in a south-west and 
north-east direction, and is nearly a mile in length, varying considerably 
in width, the maximum breadth being one-third of a mile. Its waters 
cover an area of about 99 acres, and it drains an area of nearly 2\ square 
miles. The maximum depth of 68 feet was observed near the centre of 
the loch. The volume of water is estimated at 136 million cubic feet, 
and the mean depth at 31| feet. The loch was surveyed on August 2, 
1902, when the elevation of the lake-surface above the sea was ascertained 
to be 357*35 feet. 
Dubh Loch forms a simple basin, the bottom sloping down on all sides 
towards the deepest part in the centre ; the deeper water, however, is 
found nearer to the south-western than to the north-eastern end. The 
contour-lines follow approximately the trend of the shore-line, but approach 
closer to the north-western shore than to the opposite one, indicating a 
steeper slope in that direction. Thus, near the middle of the north- 
western shore a sounding in 36 feet was taken about 30 feet from shore, 
giving a gradient exceeding 1 in 1, and towards the south-west end another 
sounding in 36 feet was taken about 40 feet from shore. The 50-feet 
basin is half a mile, and the 25-feet basin three-quarters of a mile, in 
