104 Proceedings of the Royal Society of Edinburgh. [Sess. 
a paper on the “ Freezing of Lakes ’’published in the Scottish Meteorological 
Society’s Journal for 1908.* 
The chief point of interest of the observations in the early months of the 
year, apart from the freezing of the lake, was the great uniformity in the 
temperature of the lake from top to bottom, even although considerable 
changes of temperature of the water took place from day to day. 
Table III. 
Date. 
Temperature, ° F. 
Difference. 
Surface. 
200 Feet. 
1908. 
Jan. 30 
38-3 
38-2 
- T 
Feb. 5 
37-8 
37-7 
- T 
„ 12 
38-5 
38*7 
+ -2 
„ 19 
38-7 
38-8 
+ T 
„ 28 
38-0 
38-2 
+ -2 
Mar. 3 
37*8 
37-7 
- T 
„ 10 
37-0 
37*5 
- -5 
„ 11 
36-5 
375 
- TO 
„ 12 
37-2 
37-5 
+ -3 
,, 13 
37-5 
37-5 
•o 
„ 23 
38-0 
38-0 
•o 
Apr. 2 { 
(10 a.m.) ( 
38-8 
38-8 
•o 
Apr. 2 \ 
(3 p.m.) J 
38-9 
38-9 
•o 
Apr. 3 
39-0 
39-0 
•o 
Table III. gives a few observations which illustrate this point, and the 
explanation is to be found in the mixing of the water due to winds. Thus 
on 10th and lltli March there was a calm, with the result that we do not find 
this uniformity of temperature from top to bottom. The surface water has 
been cooled down, and has not mixed with the rest of the water in the lake. 
On the other hand, on 2nd and 3rd April there were strong winds, and the 
observations show how rapidly the heat which enters at the surface is 
distributed over the whole lake. This is, I think, very good evidence that 
the currents produced by wind are appreciable to the bottom of the lake in 
the spring of the year. 
On to the end of April there was never any great variation in tempera- 
ture from the surface to the bottom. On 29th April, observations at the 
surface gave a temperature of 41 T° and at the bottom 41 ‘0°. There had, 
prior to that, been variations of as much as 1°, but these differences always 
disappeared before a strong wind. A reference to Table II. will show that 
* Yol. xiv. p. 219. 
