THE FRESH-WATER LOCHS OF SCOTLAND. 
29 
Depth 
Loch. 
Chon. 
Lochan 
Dubh. 
Loch Ard. 
Lake of 
Menteith. 
Loch Leven. 
Feet. 
May 15, 
May 15, 
Aug. 6, 
May 16, 
May 14, 
June 11, 
June 22, 
Sept. 1, 
1900. 
1900. 
1899. 
1900. 
1900. 
1900. 
1900. 
1900. 
o 
O 
o 
o 
o 
o 
o 
o 
0 
51-8 
54-7 
63 0 
51-7 
51-3 
58-7 
62-3 
58-0 
5 
58-4 
62-2 
6 
50-7 
51-1 
61-3 
51 -4 
51 T 
10 
58 -0 
62T 
12 
61-3 
50 -5 
18 
61-3 
48-5 
20 
49 -5 
50 -7 
57-5 
24 
61 -2 
48-3 
30 
60-5 
47-7 
57-4 
61-5 
35 
47-6 
40 
48 -6 
50 '5 
56 -6 
48 
50 1 
47T 
50 
56 -5 
59-3 
57 -3 
60 . 
48-5 
48-2 
46-9 
50-2 
56-3 
56-8 
56-6 
70 
56-2 
56 ’6 
76 
90 
...• 
47 -5 
46-5 
96 
47-5 
46-5 
100 
46-4 
Loch Chon and Lochan Duhh , — These lochs were sounded on the 15th 
May, 1900, when the surface temperature in Loch Chon varied between 
51°-8 and 54°-5 ; below the surface the temperature decreased gradually 
down to 48°’5 at 60 feet, so that the range observed throughout the 
whole body of water was only about 6°. In Lochan Dubh the surface 
temperature was slightly higher than in Loch Chon (54°*7), while the 
temperature of the deeper water was observed to be about 1° lower 
(47°*6), so that in the small body of water contained in Lochan Dubh 
the range was greater than in the larger Loch Chon, viz., 7°. 
Loch Ard . — Loch Ard was visited on the 5th and 6th August, 1899, 
and again on the 16th May, 1900. The highest surface temperature 
(64°*6) was observed in the southern prolongation of the loch in August, 
the maximum temperature observed at the same time in the body of the 
loch proper being 63°. It will be seen that the whole body of water 
was warmer in August, and that a drop of 10° was recorded between the 
depths of 30 and 50 feet, the extreme range of temperature from surface 
to bottom being 17°. No steep gradient was observed in May, the 
temperature decreasing gradually from top to bottom, the extreme 
range observed in May being 8°*7. 
Lake of Menteith . — The Lake of Menteith was visited on the 7th 
August, 1899, and the 14th May, 1900. No serials were taken in 
August, when the surface temperature varied only from 62°-2 to 63°*2. 
In May the surface temperature varied from 51°T to 52°-2, and the 
temperature decreased gradually from surface to bottom, the range 
observed in May throughout the whole body of water being only 2° — 
