ON THE SEICHES OF LOCH EARN. 



465 



from 12th October to 7th December showed much less seiche activity than the period 

 from 10th August to 28th September. 



In more or less settled weather, by far the commonest seiche configuration on Earn 

 is a uninodal and binodal dicrote.* This varies between the two extremes where the 

 binodal on the one hand and the uninodal on the other are scarcely noticeable ; but the 

 seiche in our observations was hardly ever either purely uninodal or purely binodal. 

 In these seiches the 5-9- configuration period caused by the interference of the uninodal 



^ J 



c~ 



<d~Crclv &ajims 



MsnJsnc-cLo , ZJ-qos: 



f"* 



*-^r 



Ho 



.10 



10-iii 



It so 



~ 3 dock ^>OA^rJJ fysisrvc-Uxj %J.q OS". 



rl 



-/ 



T 



Y 60 * lo iQ.io 



-? dcxJv fea/vrv. 3/ - q OS: 



t; 



i — 



frV 



T 



i 



n-io 



Fig. 1. 



and binodal components is usually reproduced with the most beautiful regularity, 

 sometimes for a whole day or even longer. For example, in the seiche observed at 

 Lochearnhead from 16th to 22nd October 1905, which lasted about 6|- days, say for 127 

 configuration periods, only six of these periods were found too short by one uninodal, 

 and three too long by the same amount. It is probable that the gradual change of phase 

 accompanying the rise and fall of the amplitudes of the components more than com- 



* For brevity, in what follows we shall denote such a seiche by " UB-dicrote." Similarly, " UBT-tricrote " 

 would mean a tricrote seiche with uninodal, binodal, and trinodal components ; and we shall occasionally denote the 

 amplitudes (half ranges) of these components by U, B, T respectively. 



