H(m) . 



2 4 6 8 10 12 14 16 18 20 22 24 



_ V m/sec 



Figure 6. Observed heights of characteristic 

 waves at different wind velocities. 



the average height and the upper limit of the height of succeeding 

 characteristic waves as accurately as possible. These limits are 

 indicated in figure 6 by vertical lines. A single cross (x) means 

 average heights without estimation of the upper limit. We find at 

 a wind velocity of 15-16 m/sec a variation in the height of character- 

 istic seas between about 4 and 8 m, which may be interpreted as an 

 interference phenomenon. But at higher wind velocities it is diffi- 

 cult to determine the upper limit exactly if the long rolling sea 

 interferes suddenly and the steepened high crests fall forward, 

 often forming breakers of several meters in height. 



In the open sea, successive waves always differ considerably 



22 



