.8 _L 

 20 ^ 



25 

 30 



40 

 50 



WAVE AGE,-£- 



Flgure 7. Relation between wave steepness as 

 expressed by the ratio wave height to wave length, 

 H/L , and wave age as expressed by the ratio wave vel- 

 ocity to wind velocity, C/U. Observed values shown 

 by circles. 



3. Decrease of height of swell . The height of swell de- 

 creases as the sw'll advances. Roughly, the \vaves lose one-third 

 of their height each time they travel a distance in miles equal to 

 their .length in feet. 



9. Increase of period of swell . Some authors claim that 

 the Deriod of the swell remains unaltered when the swell ad- 

 vances from the generating area, vrriereas others claim that 

 the Deriod increases. The greater amount of evidence at the 

 present time indicates that the period of tbe sv/ell increases 

 as the swell advances. 



17 



