means of the curves in Plates II to V it can be ascertained that 

 the eiuplrical relationships 1 to 6 are satisfied. 



Figure 9. Wave steepness (upper graph) , expressed 

 by the ratio H/L, as function of distance from coast 

 line at 10^, 20li, and 30^ after a wind of 30 knots 

 started to blow over an undisturbed water surface, and 

 corresponding representation of wave age (lower graph) 

 expressed by -the ratio of v/ave velocity to wind vel- 

 ocity, C/U. 



According to Figure 9, with a 30-i:not wind the wave veloc- 

 ity remains lower than the wind velocity at fetches of 600 miles 

 or shorter. With increasing fetch the wave velocity v.'ould , how- 

 ever, exceed the wind velocity and the waves would continue to 

 grow in height but decrease in steepness. 



If the wave velocity exceeds the wind velocity the v-aves 

 can no longer receive energy bv push but will lose energy because 



25 



