24 



Fisher// Board for Scotland. 



very complex wave, or parts thereof, are almost innumerable ; and we 

 must be very careful indeed before we ascribe any one of them to a 

 single definite physical cause. Unless we keep well in mind this latter 

 precaution, we may, so to speak, be doing no more than verifying 

 Fourier's theorem, and demonstrating the fact that any function 

 whatsoever may be expressed in a series of sine waves. 



In yet another direction has search been made for a cause which 





"5 55 

 o '-' 

 S -^ 



^ C 



<| '3 



t a 



S o 



CSrC 

 03 O 



C to 



o e 



>^ S 



— V oi C 





<1 o 



S g 





should account for our phenomenon. Professor Otto Pettersson 

 has tm'ned from local meteorological conditions, in order to seek 

 a cause in a variation of the great oceanic currents and especially of 

 the " Gulf Stream," and to correlate these in turn with long-period 

 astronomical phenomenon. We have some knowledge * of a seasonal 



* Cf. Cleve, Ekmann, and Pettersson, Les variations annudlcs de I'eau de 

 surface de rocean Atlantique. Gotebovg, 1901. 



