Plates II to V shovj only the highest waves present. These 

 waves have traveled the entire distance froiri the beginning of 

 the fetch. However, the wind can raise new waves anywhere in 

 the fetch, and some of .these may grow slowly and reach heights 

 corresponding to the distances th-ey travel, while others may 

 grow rapidly and break. These contribute to the broken ap- 

 pearance of the sea surface v;hich is described as the "state of 

 the sea." The relationship between the wind and the state of 

 the sea is discussed later. 



DECAY OF WA7E3 

 Waves Advancing into Regions of Calm 



When waves spread out fro^a a generating area into a region 

 of calm only half of the energy of the wave advances with wave 

 velocity. The consequence of this characteristic can be recog- 

 nized by. examining a simple example. Assume that a series of 

 waves is foriied by rhythmical strokes of a wave machine which 

 at each stroke adds the energy E/2 in a given locality. The 

 first stroke creates a wave of energy E/2. In the time interval 

 botween the first and the second stroke one half of this energy, 

 E/Z,., advances one v^ave length and one half, E/4, is left behind. 

 The second stroke adds E/2 to the part of the energy which was 

 left behind. On completion of the second stroke two waves are 

 present, one close to the wave macliine with an energy 3E/4 and 

 one which has advanced one wave length with energy E/4. By re- 

 peating this reasoning. Table II has been oreoared, showing the 



27 



