198 Long Waves in Canals and Standing Waves in Closed Basins 

 Table 26. Theoretical free periods of the Baltic 



velocities caused by the oscillation, do not occur in the centre of the basin 

 ne?r the nodal line, but at the points where the cross-section narrows, at 

 the Darser sill and at the entrance of the Gulf of Finland. 



too 



80 

 40 



-40 



£ -80 



120 



-160 

 -200 



8 

 a 

 



-4 



_ 8 g 



-12 



-16 

 -20 



4 8 12 16 20 24 28 32 36 40 44 48 52 



Sections 



Fig. 86. Theoretical distribution of the vertical (2iy ) and horizontal (2£ ) displacement 



of the uni-nodal oscillation of the Baltic — Gulf of Finland (T = 27-5 h). 



The important question is, to what extent the Beltsea participates in the 

 oscillatory process of the Baltic. Neumann has been able to prove that, 

 according to observations, this oscillation process does not continue into 

 the Bay of Kiel. The bays west of the Darser sill participate only in the process 

 in so far as, in the first half of the oscillation, they simply fill up, whereas 

 in the second half they are again emptied. We have here a practical application 

 of the case which was dealt with theoretically on p. 177. If we designate the 

 Baltic as basin 1, the Darser sill as the connecting canal 2 and the basins 

 east of the same as basin 3 (see Neumann, 1941) we obtain from the equation 

 (VI. 85) as the fundamental period of the system Gulf of Finland — Baltic — 



