TEMPERATURE OF SCOTTISH LAKES 
93 
his Presidential Address to the Royal Society of Edinburgh in 1872/ 
observations which he had made in Lochs Lomond, Tay, and Katrine 
during the years 1870 and 1871. Sir Robert Christison demon- 
strated the existence in these lochs of a substratum of relatively cold 
water of considerable thickness, which underwent little or no seasonal 
change. He also noted the existence of a discontinuity between the 
temperature of the upper and lower layers of water, which has been 
found to play such an important part in the temperature of fresh- 
water lakes. 
Dr Buchan ^ next interested himself in the observations of 
Jardine and Christison, and by a comparison of the temperature of 
the cold substratum with the mean temperature of the air, he arrived 
at the conclusion that it is the mean temperature of the cold half 
of the year which determines the temperature of the lowest stratum 
in deep lochs. 
On the return of the Challenge7' Expedition Mr J. Y. Buchanan 
took up the study of lake temperatures, and his explanation of the 
manner in which ice is formed on lakes was another step in the 
advance of limnology. But perhaps the most important contribution 
to the literature of the subject during last century was Sir John 
Murray's paper, published in 1888, on the effect of winds on the 
distribution of temperature in the sea and fresh-water lochs of the 
west of Scotland.^ Dr John Aitken was interested in Buchanan's 
observations, and drew attention to the importance of wind currents 
in reducing the temperature of lakes considerably below the maximum 
density point before freezing took place, and may justly be considered 
one of the pioneers of lake-temperature investigations ; but previous 
to Sir John Murray's investigations very little account was taken of 
the effect of wind on the temperature distribution of lakes, and 
Continental limnologists do not yet seem to have realised the import- 
ance of the facts brought to light by him. From that date onwards 
there has been a considerable quantity of observations, made, amongst 
others, by Sir John Murray, Mr J. Y. Buchanan, and Dr H. R. Mill, 
which materially add to our knowledge of the distribution of tempera- 
ture in lakes. 
About the year 1897 the late Mr Fred. P. Pullar began a system- 
atic survey of the lochs of Scotland in conjunction with Sir John 
Murray, and their scheme of work included an examination of the 
temperature conditions of various lochs surveyed. After his death 
1 Froc. Roy. Soc. Edin., vol. vii. p. 567. 
2 Op. cit. 
^ Hcott. Geogr. Mag., vol. iv, p. 345. 
" The Distribution of Temperature under the Ice in Frozen Lakes," Proc. 
Roy. Soc. Edin., vol. x. p. 409, 1880. 
