formation will be damped out faster. It is well known that a rough 

 sea can be calmed to a certain extent by whirling water which is 

 upwelling on the windward side of a drifting ship. This "natural" 

 kind of wave decay is often used by captains of ships which have to 

 lie to when caught in storms. Lying athwart or nearly athwart to 

 wind and sea, the ship slowly drifts to leeward, causing by its 

 motion a zone of upwelling water to windward. This whirling, up- 

 welling water is an additional source of turbulence and energy dis- 

 sipation with regard to the local wave motion and acts - as exper- 

 ience shows - as a damper on waves, and at first the steep breaking 

 waves are damped. It is this whirling water caused by the drift 

 of the ship which destroys to a certain extent high and heavily 

 breaking seas mostly far away from the ship to windward, or far 

 enough not to become too dangerous for the ship. At lower wind 

 velocities the same effect of upwelling water is to be observed, 

 and during the voyage with the "Heldberg" these additional effects 

 of turbulence could be studied when the ship drifted southwest of 

 the Azores for several days with engines stopped. At a wind velo- 

 city of 8 to 10 m/sec the relatively small but steep waves of the 

 common run were breaking about 50 ffl to 100 m windward of the ship 

 and the upwelling water in the drifting path near the ship was al- 

 most free of larger breaking waves. 



Similar effects of additional turbulence are also to be ob- 

 served in the wake of ships under way. This is moat striking In 

 the case where a slight breeze causes smaller waves or ripples at 

 the sea surface and the sun shines on the water. One can follow 

 the wake of the ship over rather long distances as a nearly smooth, 



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