276 
BATHYMETRICAL SURVEY OF 
Depth in 
feet. 
August 11, 1901 
(R. M. Clark). 
August 23, 1901 
(R. M. Clark). 
September 2, 1901 
(R. M. Clark). 
August 21, 1902 
(Lake Survey). 
° Fahr. 
° Fahr. 
° Fahr. 
° Fahr. 
0 
63-5 
61*9 
58-4 
5 
61*9 
10 
620 
58T 
20 
61 -5 
57-6 
25 
59*4 
57*3 
56-0 
30 
52 0 
54-9 
35 
46-0 
50-9 
40 
46-0 
44 0 
45-9 
48*0 
50 
43-2 
43-2 
46 0 
55 
42-8 
42-8 
00 
42-8 
42-8 
70 
42'3 
100 
44-9 
These serials indicate a most remarkable range of temperature — a 
range amounting to 21°*2 from the surface to a depth of 70 feet on 
August 11, 1901, and 19°-1 from the surface to a depth of 60 feet on 
August 23, 1901 ; the range observed in 1902 was much less, viz., 13°’5 
from the surface to a depth of 100 feet. Down to a depth of 25 feet the 
readings were higher in 1901 than in 1902, but beyond that depth the 
temperature was lower in 1901 than in 1902. The greatest fall of 
temperature was observed between the depths of 25 and 40 feet in both 
seasons, but the decrease of temperature within this interval of 15 feet 
amounted in 1901 to 13°‘3 and 13°’4, while in 1902 it amounted only to 
8°. The only observations that may be compared, as regards range 
of temperature, with these in Loch Achilty, were taken in Loch Mon- 
zievaird* in the Tay basin on June 8, 1903, when the range amounted 
to 20°-6 from the suriace to a depth of 36 feet, and when a fall of 
temperature equal to l°-5 per foot of depth was observed between 5 and 
15 feet. The temperature conditions observed in Loch Achilty (as well 
as in Loch Monzievaird) may probably be ascribed to — (1) the com- 
paratively great depth, (2) the. comparatively small drainage area, 
and (3) the sheltered position, the thickly wooded shores tending to 
temper the force of the winds blowing across the surface of the water. 
Mention may here be made also of the large range of temperature 
observed in the little Loch Dubhf in the nan Uamh basin on July 12, 
1902, when the range amounted to 15|° from the surface to a depth of 
100 feet ; it is possible that under favourable weather conditions, and 
later in the season, the range of temperature in the waters of Loch Dubh 
may equal that observed in Loch Achilty. 
See p. 120. 
f See p. 266. 
