573 
of Edinburgh, Session 1871 - 72 . 
as to warmth ; but there was a large proportion of sunshine, and 
little rain, till three days before, when there was 
a heavy fall 
with an easterly wind. 
The temperature on land, 
within fifty 
yards of the water, was 
made at 2 p.m. : — 
55°. 
The following observations were 
Surface, . 
44° -5 
150 feet, . 
42°-7 
25 feet, . 
43°-7 
175 „ . . 
42°-6 
50 „ . 
43°*5 
200 „ . 
42°-5 
75 „ . . 
43°-2 
250 „ . . 
42°*4 
100 „ . . 
43°T 
300 „ . 
42°T 
125 „ . . 
42°-8 
574 l . . 
42°*1 
The thermometer in Adie’s cistern, when brought up full of 
water from the bottom, but raised rather deliberately, stood at42 0, 5. 
It appears, from these and the preceding observations, that in 
the deep parts of Loch Lomond there is a substratum of water of 
several hundred feet, which, between the end of September last 
and 10th April, has been steadily of the temperature of 42° ; and 
that during last winter no other change has taken place, in relation 
to temperature in or near it, than that the level of the cold sub- 
stratum rose in the interval between 70 and 100 feet. A winter, 
materially colder than the last unusually mild one, would at least 
raise that level still nearer the surface. Whether it may reduce 
the temperature still lower than 42°, is a question which remains 
to be decided by future observation. It is still also a matter for 
observation, whether the temperature of the substratum may not 
rise a little during summer. For it may be reasonably said, that 
the unusually hard winter of 1870-71 might have lowered the tem- 
perature of the substratum in April of last year below that observed 
in April of this year after a very open winter, and, consequently, 
under 42°, which was the temperature observed in October. But the 
difference, if any, cannot be considerable ; for it can only arise from 
the heating power of the earth on which the water rests. 
The water of a lake is heated in summer and autumn in three 
ways — the heat of the atmosphere, that of the sun’s rays, and that 
of the earth. The atmosphere will communicate its heat to so 
much of the superstratum only as is disturbed, more or less, by the 
wind ; and, therefore, cannot penetrate many feet. The tempera- 
