fetch, T-p,, the reduction factor to be applied to the wave height 



at the end of the fetch and the travel time (In hours) are read off. 



Example 



At end of fetch: 



Wave height 18 feet 



Period 9 seconds 



Distance of decay .... 600 naut . .m. 



Reduction factor to be 



applied to wave height. . 0.47 



Travel time 40 hours 



Height of swell 8.5 feet 



From Inset II In Plate VI the factor Is found by which the 

 wave period at the end of the fetch, T_,, must be multiplied In 

 order to find the period of the swell at the end of the distance 

 of decay . 



Example 



Wave period at end of fetch . . 9.0 seconds 

 Reduction factor to be applied 



to wave height 0.47 



Factor of period Increase (from 



Plate VI, Inset II) ... . 1.27 

 Period of swell 11.4 seconds 



From Inset I In Plate VI are found velocity and length corres- 

 ponding to any given wave period. Exact values are obtained by 

 using the formulas: G (In knots) = 3.03 T, L (In feet) = 5.2 T . 



Example 



Period Velocity Length 

 seconds) (knots ) ( feet) 



Waves at end of fetch 9.0 27-5 415 

 Sv/ell at end of distance 



of decay 11.6 35.0 690 



46 



