the wavelets take on a "glassy "appearance. The wavelets have ex- 

 ceeded the Initial state. They become -unstable and "break up" at the 

 crests. This "break up" rather soon changes to a distinct "break 

 over" when the wind speed increases, and observations show that at 

 a wind velocity of about 150 cni/sec the crests of the fully developed 

 ripples clearly fall forward. The wave length of these small "break- 

 ing" waves is about 20-25 cm. In the further development of wind 

 generated waves into the state of real ocean waves, the turbulence 

 which is now present and connected with the breaking unstable waves 

 in all phases plays an important role. This turbulence (which implies 

 energy dissipation) increases rapidly with increasing wind velocity. 



The first attempt to calculate the growth of ocean waves due 

 to the action of wind at different stretches of water over which the 

 wind has blown (the fetches) and at different durations of wind 

 action, was made by H, U, Sverdrup and W. H. LIunk [1]. It was the 

 first approach to a scientific basis for this special problem of 

 great practical importance. Until this remarkable work, the results 

 of which have partly been used in practice since 1942 and which was 

 published in its final form in 1947, no one had attacked the com- 

 plicated problem of wave forecasting. This first attempt incited 

 further investigations both on theoretical and empirical bases, so 

 that new ideas and more comprehensive observations were soon forth- 

 coming. Even if we know today that some of the assumptions made 

 in this treatise do not hold or are an oversimplification of the 

 mechanism of wave generation, this first attempt has its value as 

 a pioneer work because it stimulated further research and new 

 approaches, like this report, and presumably other scientific work 



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