254 
BATHYMETRICAL SURVEY OF 
under half a mile, its maximum breadth one-sixth of a mile, and its 
mean breadth one-tenth of a mile. Its waters cover an area of about 32 
acres, and it drains an area eight times greater, or about 262 acres. 
Sixty-five soundings were taken, and the maximum depth observed was 
153 feet, which bears the ratio to the length of the loch of 1 to 15. 
This low ratio is only equalled by the little loch on Eilean Subhainn 
in Loch Maree, and the loch which most nearly approaches it is Loch 
Fender in the Tay basin, in which the ratio is as 1 to 22, followed by 
Loch Dhugaill, near Kishorn, in which the ratio is as 1 to 27. Among 
the larger Scottish lochs, the nearest approach is found in Loch Treig, 
with a ratio of depth to length of 1 to 62. The volume of water 
contained in the loch is estimated at 86,956,000 cubic feet, and the mean 
depth at nearly 63 feet, or 41 per cent, of the maximum depth. The 
loch was surveyed on July 12, 1902; the elevation of the lake-surface 
above the sea was found, by levelling from bench-marks, to be 103-0 
feet ; when visited by the Ordnance Survey officers on August 6, 1869, 
the elevation was 103*3 feet above sea-level. No drift-marks were seen, 
but the keeper stated that the annual range in level was about 9 inches. 
Loch Dubh is very simple in conformation, the contour-lines follow- 
ing approximately the shore-line. Near the north-west end there is a 
slight rise of the bottom, as shown in section A-B on the map, but 
otherwise the lake-floor slopes down regularly to the deepest part, 
which lies towards the north-eastern shore. The maximum depth of 
153 feet was observed at a distance of about 120 feet from this shore, 
giving a slope of 59° ; the height of the hill immediately adjoining is 
240 feet, and the slope 35°, hence the slope from the top of the hill to 
the bottom of the loch is one of 45°. The areas between the consecutive 
contour-lines drawn in at equal intervals, and the percentages to the 
total area of the loch, are as follows; — 
0 to 50 feet 
14-8 acres 
407 per cent. 
50 „ 100 „ 
8-9 „ 
30-9 
>> 
o 
p— H 
o 
o 
7-6 „ 
26-5 
J > 
Over 150 ,, 
0-5 „ 
1-9 
>> 
31-8 ,, 
100-0 
>> 
Temperature Observations . — A most interesting series of temperatures 
was taken in Loch Dubh at the time of the survey, as given in the first 
column of the following table. The loch was revisited in March, 1903, 
when the water was found to be uniform in temperature from surface 
to bottom, as given in the second column of the table — 
