friction or eddy viscosity would give too rapid a decrease of 

 wave height, and that it would be necessary to introduce a smaller 

 coefficient applicable only to wave motion. These conclusions are 

 not quite clear and perhaps not admissible. If in the upper layers 

 of the water where wave motion takes place, a certain state of 

 turbulence is present, this "disordered motion" superimposes itself 

 upon the regular wave motion too, without regard to the causes of 

 this "disordered motion." (See the notes on observations in the 

 wake of ships underway and in the windward upwelling water of drift- 

 ing ships.) In comparison with this "turbulence" all secondary 

 effects of eddy viscosity, which are smaller than this "turbulence" 

 (including molecular viscosity) may be neglected. L. Prandtl [l6] 

 states: "Man kann annehmen, dass wenn zwei Ursachen vorhanden sind, 

 die einen Austausch hervorbringen, der wirklich eintretende Aus- 

 tausch ungefahr mit dem grBsseren von beiden AustauschbetrSgen 

 Ubereinstimrat." 



Our present knowledge of turbulence in the surface layers of 

 the ocean at different stages of wave development is very meager, 

 and we have to suppose that this turbulence depends to a certain 

 degree on other oceanographical and meteorological conditions. 

 Oceanographic observations indicate that the coefficients of eddy 

 viscosity are about 1,000 to 100,000 times as large as the ordinary 

 viscosity coefficients. Assuming that dissipation takes place by 

 ordinary viscosity only, the effect of friction is neglected in 

 the energy balance by Sverdrup-Ii/funk. These authors explain the 

 observed decay of waves only as the effect of air resistance against 

 the advancing wave. When wind-generated waves spread out from the 



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