184 Long Waves in Canals and Standing Waves in Closed Basins 



of its level. As an example of such oscillations, Fig. 77 shows simultaneous 

 registrations at both ends of the lake. It shows the uninodal seiche, and it 

 can be noticed how the displacements of the water level at one end are the 

 mirror image of the displacements at the other end. 



22 24 2 

 

 5 12 1913 



8 10 12 14 16 18 20 22 24 2 4 

 

 612 1913 



6 8 



Fig. 77. Simultaneous recordings of the uni-nodal seiche in Lake Vattern at Bastedalen 



and Jonkbping. 



Bergsten divided the lake (Fig. 78) in four parts, and could very well 

 approximate the normal curve, by means of parabolical and quartic curves 

 and then apply Chrystal's method for the determinations. The result can be 



dbnkoping 

 SO 2 



flstersuna 

 20 22 24 26 N 



Fjg. 78. Normal curve of Lake Vattern and its approximation by parabolic and quartic 



curves (broken) (Bergsten). 



found in Table 23. The mean period of the uni-nodal seiche is 178 99 min, 

 the extreme values of the single series are 180 8 and 174-6 min. The differences 

 are caused partly by the different height of the water level at the time of the 

 observation, and partly by the difficulty in determining correctly the phase 

 of the first and the last wave of the series. There is a discrepancy of only 6 % 

 between the observed mean value and the theoretical value, which is reduced 

 to 0-2%, if friction is taken into account by determination of the damping 

 coefficients. For the multinodal seiches the agreement becomes worse, but 

 even for the five-nodal seiches the discrepancy does not exceed 4%. These 

 discrepancies may be caused by the difficulties in establishing the period of 

 oscillation of these shorter waves. 



