steady wind conditions were collected and related to the measured 

 wind speed. In this way, about 27,000 single observations have been 

 placed together in a set of more than 250 "series," comprising the 

 range of wind velocity between 2 and 22 m/sec. Separated from these 

 series, further sets of wave measurements at limited fetches were 

 gathered which will be used in Chapter II. 



The single measurements of each series were utilized by count- 

 ing the frequency of the observed periods, taking period intervals 

 of 0.5 seconds, and then representing them in diagrams showing the 

 frequency distribution of periods at a certain locality and at a cer- 

 tain wind speed. Observations under conditions with rapid wind 

 changes are here omitted. This method of counting time intervals 

 between succeeding crests naturally provides no exact mathematical 

 analysis of water level fluctuations or of time series in general. 

 But it seems to be useful just for practical purposes. The result 

 provides a realistic picture of sea surface state, showing the per- 

 iods which are to be expected in the cha r acteristic composite wave 

 pattern, the range of periods under different conditions, and the 

 more or less frequent appearance of periods in certain "bandsl' 



In the composite wave pattern the rather steep "breaking sea" 

 was the most conspicuous undulation as long as the sea surface was 

 under the Influence of generating winds, whereas the superimposed 

 smaller waves, as random components, did not disturb this pattern 

 or influence it essentially. But the heights and periods of succeed- 

 ing waves at a fixed locality mostly scattered through a large range, 

 and in the ever-changing wave patterns of the sea surface longer waves 

 with greater periods appeared occasionally, clearly marked by smaller 



12 



