It follows that there is a lower limit of wind velocity below which 

 waves will not be generated „ The change in the wave amplitude with 

 time is computed from a consideration of the difference of the energy- 

 supplied and that dissipated by the wave with respect to time, and 

 can be expressed in the following forms 



*f - f 4^>*i S Hxh) - ( aw *+ X #«* ) a po) 



d t *- ? ff ^ [ sihh(Z-x'h) 



Integration of equation 20 gives: 



t~ ~L i n £lz£jl*' (21) 



?2 C,-C Z CL 



where a' is the wave amplitude at the begin ning of the time interval 

 and Cl . |£'f^ ^Cm.ZVX** * ^SM 



Experimentally it has been shown that there' is a definite maximum wave 

 amplitude for a given wind velocity which cannot be exceeded regardless 

 of the duration of the wind velocity. 



The author deduces that any wind with a velocity greater than 69.5 

 cm, per second is capable of generating waves, and the combined effect 

 of capillarity and gravity produces two separate wave trains „ Table I 

 gives the computed values of the length and height of waves of maximum 

 steepness that can be generated in depths greater than the wave length, 

 by winds with velocities from 70 to 122.7 cm. per second „ 



TABLE I 



7) 



m (cm/sec) 70 80 90 / O O 



X (cm) : 2.05 1.45 2 3.71 0.80 : 5.19 0.57 



& (cm/sec) ; 23.3 % 26.9 % 30.0 



a </z i 0.00782 ■ 0.01590 : 0,0254 



: 0.00591 : 0.00343 : 0.00279 : -#¥§§5£L 6. OC3L 2 // 



2 a = H (cm) % 0,032 0.017 : 0.118 0.0055 % 0.264. 0.0032 ; 0.49 0.0022 



v n> (cm/sec) 122.7 



X (cm) : 10 .4-6 0.28 : 



& (cm/sec) % 41.2 : 



a o/% Q 1 0.069 0.00184: 



2 a Q = H (cm); 1.444 0.0010 : 



27 



