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Proceedings of the Royal Society of Edinburgh. [Sess. 
where 
3 (*)« 
b(x) 
A{x) A'(x), 
b(x) being the breadth of the surface of separation at a distance x from the 
origin, A(x) the area of a cross-section of the portion of the lake below the 
surface of separation, and A'(x) of a cross-section above the surface of 
separation. The other symbols have the meaning assigned by Professor 
Chrystal in his memoir on the Hydrodynamical Theory of Seiches, Trans. 
Roy. Soc. Ed/m., vol. xli. (in.), p. 599, and the above equation is of the same 
form as Professor Chrystal’s equation for the ordinary seiche. 
Part III. 
A temperature normal curve was drawn for the Madtisee and approxi- 
mated to by a single parabola. The period of the temperature seiche 
calculated in this way was 24'8 hours. A second calculation, deduced from 
the known period of the ordinary seiche by considering the analogy between 
the ordinary seiche and the temperature seiche, gave 24 hours. 
Part IV. 
Laboratory experiments were carried out by Mr Wedderburn and Mr 
Williams to test the foregoing theory, and gave conformable results. Tanks 
of various shapes were used to imitate different shapes of lake basins, and 
difference of density was obtained by using a layer of paraffin resting on a 
layer of water. 
(. Issued separately February 23, 1911.) 
