of 1950. But the difference does not seem to be very important. 

 Formula (la) will be derived in Chapter II. 



The periods of the fully developed "longer waves" are, as it 

 seems, fairly well approximated by a linear relation 



TgCsec) = 1^ = F" Pm'^ " 0-^77v (v given in m/sec) (2a) 



This relation is based on the assumption (J^ = 1.37 v as sug- 

 gested by empirical evidence and already used in the papers of 

 Sverdrup and Munk [1], and of Neumann [8], At present, it is diffi- 

 cult to say whether this relation is exactly a linear one, or whether 

 there is a slight curvature. But possible deviations from the linear 

 proportionality as given by (2a) seem to be of the second order. 



The period T^ in Fig, 5j although not always clearly separated 

 from T-, or Tp, indicates an intermediate wave with a velocity of 

 phase propagation very near to the wind velocity. The broken line 

 T^ in Fig. 5 is calculated by taking (3^ = v and represents the re- 

 lation 



T-^(sec) = ~ V = 0.64 V (v given in m/sec) (3a) 



These three waves which presumably dominate the composite sea 

 surface pattern in fully or nearly fully developed state may be 

 called 



1) the "sea" (T^), or p^^-wave ( (J^/v = ^^) 



2) the "longer wave" (T2), or p*-wave ( ^"2/^ = Pj) 



3) the "intermediate wave" (T^), or p(l)-wave ( (J^/v = 1) 

 The periods and wave-lengths of these three waves are given in 

 Table 1 at different wind velocities up to 24 nv^sec. 



20 



