of Edinburgh, Session 1878 - 79 . 
69 
Depth in 
Feet. 
Temperature Fahr. 
at Station 
No. 6. 
No. 7. 
3 
36*00 
36*00 
6 
36*60 
36*80 
12 
37*35 
37*50 
18 
37*35 
37*80 
21 
37*80 
24 
37*50 
38*15 
30 
37*90 
38*30 
36 
38*45 
39*00 
42 
39*80 
40*70 
45 
42*00 
Mud, 48 
41*70 
( 42*00 
} 42*05 
From these observations we have the mean temperature of the 
48 feet of water 37*83° on 25th January, and 38*28° on the 1st 
February. The heat required to produce this rise of temperature 
is very considerable, and would require the combustion of very 
nearly two tons of coal per acre. 
It was shown that the mineral constituents of this water were 
insufficient to produce a lowering of its temperature of maximum 
density : it was, however, uncertain whether this effect might not 
have been produced by the substances which gave the water its 
peculiar odour. The actual temperature of maximum density of the 
water was accordingly compared with that of distilled water in the 
same piezometer, and no difference could be detected. 
Hence it was evident that, before being completely frozen over, 
Linlithgow Loch must have been cooled down throughout to a mean 
temperature of certainly two degrees lower than that of its maximum 
density. As this conclusion was at variance with the generally 
accepted doctrine, it was necessary to test it by observations in 
another lake, and in one of undoubted purity. The result of obser- 
vations made with this purpose in Loch Lomond on the 28th and 
29th January was that the general lowering of temperature was 
even greater than in Linlithgow Loch, the mean temperature under 
the ice at a spot 51 feet deep being 34*05° F. Observations under 
the ice were made at four stations between Ealloch and Luss, and 
several observations were made in the water off the edge of the ice, 
VOL. x, 
K 
