606 Proceedings of the Royal Society of Edinburgh. [Sess. 
the suggestion of an internal seiche, communicated by Sir John Murray, was 
the correct one.* 
It is, of course, possible that the oscillations may be to some degree forced 
by tidal influences, and there is nothing new in the idea of a forced seiche, 
as Dr Pettersson seems to think, j- 
Pettersson adds, that whatever may be the main cause of the phenomena, 
there can be no doubt of their influence upon the fish-life and the fisheries 
of our seas. In 1877, G. Ekman discovered that herring shoals vanisiied 
suddenly from the Swedish fjords and from the coast bank whenever the 
ice-cold Baltic water accumulated there. In 1909, the greatest fish catches 
were made from 1st to 6th February and from 20th to 23rd February, when 
the warm and salt deep water had its periods of flow. In the ebb periods 
the fishery was almost nil, and ceased altogether about 27th February. 
It may be some satisfaction to people who think that scientific work 
should not be undertaken without a practical end in view, to know that the 
temperature observations made by the Scottish Lake Survey may bear 
fruit in a better understanding of the movements of herring shoals. 
* I am indebted to Dr H. R. Mill for a report of this meeting. 
t See Chrystal, “ Hydroclynamical Theory of Seiches/’ Trans. Roy. Soc. Edin ., vol. xli., 
part iii., p. 608, 1905 ; also ibid., vol. xlvi., part iii., p. 514. 
( Issued separately August 14, 1909.) 
