2 
Proceedings of the Royal Society of Edinburgh. [Sess. 
I — An Experimental Investigation of the Temperature Changes 
occurring in Fresh- Water Lochs. By E. M. Wedderburn, 
M.A, LL.B. 
(Read June 3, 1907. MS. received July 8, 1907.) 
Introductory. 
In a previous communication published in the Transactions of the Society 
(vol. xlv., part ii., p. 407) I attempted to discuss the temperature observa- 
tions made in Loch Ness during the years 1903 and 1904. Some of the 
conclusions which I arrived at have not been generally accepted, and in 
particular limnologists have been slow to acknowledge the existence of 
the temperature seiche first described by Mr Watson, and which I consider 
was fully borne out by the observations published in my previous com- 
munication.* In order to get some ocular demonstration of the possibility 
of such a phenomenon, I had recourse to laboratory experiments, and it 
is the description of these experiments which is the main object of the 
present communication. Besides demonstrating the nature of the tempera- 
ture seiche, the experiments also throw light on the formation of what 
has been called by German and Austrian writers the Sprung schicht, 
and which I now propose to call in English the “ discontinuity layer,” 
which, with the word Sprung schicht, has the merit of being descriptive. 
Current systems were also studied experimentally. There is, of course, 
always a great doubt as to how far small-scale experiments in a case of 
this kind are applicable, and I do not pretend to say that accurate deductions 
can be drawn, or quantitative results obtained, from the experiments which 
have been made. They were, however, very suggestive of ideas, and for 
that, if for no other reason, they merit description. 
Before proceeding to a description, I wish in the first place to state 
briefly the cycle of temperature changes occurring in fresh-water lochs, in 
order that it may be understood what the phenomena are which require to 
be experimentally produced. 
It has been recognised generally that there are three distinct phases in 
the cycle of temperature changes in those lochs which, following Forel’s 
classification, are of the Tropical type — that is, in those lochs the tempera- 
* See Pet. Geogr. Mitt., L.B., p. 170. 
