186 Long Waves in Canals and Standing Waves in Closed Basins 



in which T x and T 2 are the periods of partial oscillation, when each basin is 

 assumed to be completely closed at the connecting canal q. These periods 

 can be determined accurately by using one of the methods previously ex- 

 plained, and then it is not difficult to determine the period of the oscillation 

 of the connected system. 



Examples are the Hallstattersee (Salzkammergut, Austria), the Konigssee 

 and the Waginger-Tachinger See (Bavaria) and others which consist of two parts 

 connected by a more or less narrow canal. The computations made by Neu- 

 mann of the period of the connected system have shown that there is a very 

 satisfactory agreement between the observations and the theory (see Table 24). 



Table 24. Lakes composed of two inter-connected parts 



(l and b in km, h in m, S in 1000 m 2 ) 



Period of oscillation 



Computed 



Observed Endros 

 1905, 1906, 1927 



Hallstattersee 



Southern Basin: / x = 5-47 

 Northern Basin: l % = 2-79 

 Connecting Canal: / = 0-20 



Konigssee 



Northern Basin: l y = 5-28 

 Southern Basin: h = 2-22 

 Connecting Canal: / = 0-38 



Waginger-Tachingersee 



Wagingersee: /j = 6-9 



Tachingersee: L = 3-9 



Connecting Canal: / = 014 



b x = 108 

 b, = 0-72 

 b = 0-40 



/; x = 81-0 LSi= 87-5 



h 2 = 23-0 

 /* = 13-6 



S 2 = 16-5 S 



bi = 0-69 5 /»! = 1 14-5:5! = 79-54) 

 b, = 0-64 4 h 2 = 59-SS, = 38-5 

 b = 0-27 q = 8-1 j 



/>!= 1-123 

 b, = 0-683 



i h = 141 



l h = 8-8 

 q = 009 



S x = 16-82 

 5 2 = 603 



16-25 



110 



64 



16-4 min 



10-6 min 



about 62 min 



The damping of the seiches in lakes permits one to estimate the influence 

 of friction on the oscillation. Endros (1934, p. 130) has given a compilation 

 of the logarithmic decrements of the seiches of many lakes, part of which is 

 reproduced in Table 25. It shows that there is a great variation in logarithmic 

 decrements, ranging from the smallest value of 0015 in the Lake of Geneva 

 to its twenty-fold, viz. 03 10 in the Waginger-Tachinger See. Therefore, the 

 successive amplitudes decrease for the Lake of Geneva by 0-3%, for the 

 Waginger-Tachinger See by 48%. The values of the damping factor |/3 = 

 = 2/i/T show still greater variations. Leaving the large value of a fish-pond near 

 Freising out of consideration, the Lake of Geneva has again the smallest value, 

 viz. 0-4 x 10 _3 min _1 , the Konigssee the fifty-fold of this, viz. 19 6 x 10~ 3 

 min -1 . It can be concluded from the compilation by Endros that the strongest 



