the striking contrast between extremely high waves and lower ones 

 is smoothed out. The waves at the sea surface now show a more 

 irregular pattern without distinct groups, until after some time 

 new groups of waves may arise. 



When discussing the results of observations in Section 2, a 

 large scattering of periods over a certain interval was pointed 

 out. Scattering periods are to be expected in any way when con- 

 sidering the resultant interference patterns of waves, and the ex- 

 ample in Fig. 7 shows these different time intervals between suc- 

 ceeding crests by horizontal arrows. Thus at the place x = after 

 passing the high crest at t = 2.8 sec, we would observe the next 

 crest after 9.2 sec and the following crests after 7.0j 14.9 (double- 

 wave," 7,7'^ 7»2)', 10.2} 9.0; 8.0} 14.0; 10.1} 8.6} 8.4 seconds and 

 so on. These periods are to be compared directly with the represent- 

 ation of the observations in Fig. 3> obtained at a wind velocity of 

 16 m/sec in fully developed wave motion. 



Fig. 8 represents some profiles of wave patterns, showing the 

 variations of dominant waves with space and time at v = 16 m/sec. 

 The wave profiles are computed for time intervals of 3 seconds and 

 extend over a distance of l600 m as shown by the scale of distance 

 at the upper horizontal line. 



By means of these profiles some outstanding features of complex 

 wave motion may be explained. For example, we find the striking wave 

 a, at t = at the place x = 350 m, but, when progressing, this wave 

 decreases in height very rapidly as indicated by the dashed line 

 which is drawn from A downwards to the right hand side. After 15 

 seconds this wave has moved about 200 m farther and is to be found 



30 



