have to be found. The values of H^,, and H^,,, are obtained from 

 Plate VI by entering the graph with the period at the end of the 

 fetch, T-n,, and the partial distances of decay, D' , and D" (see 

 Table V). The corresponding periods, T^, and Tj^„ , are obtained 

 from Inset II to Plate VT in the manner described above. Having 

 determined these quantities, Hj.„ y, is obtained from Plate VII 

 in the following manner: 



The average value of T^, and T^„ is computed and called 

 T. The ratio between the wind velocity in the second wind 

 area, U' , and the average period, T, is found and is taken as 

 positive for a follov/ing v/ind and negative for an opposing wind . 

 From Plate VII which is entered with the ratio U'/T and the ratio 

 Hj^„/n^, a correction factor, Hj^„ y,/H^„, is read off. Multiply- 

 ing this factor by H^,, the value of H^^,, y, is found. 



Finally, H-j, y, is obtained from. Plate VI by entering this 

 graph with the period T^„ and the distance (D - D")- 



If the second wind area extends over the entire distance of 

 decay or if there is only one region of calm (see Table V) the 

 procedure is shortened, as evident from the following examples. 



Example 1 (Table V, special case a) 



Wave height at end of fetch, H^, . . 18 feet 

 Wave period at end of fetch, Tz, . . 9.0 seconds 

 Distance of decay, D 600 naut . m. 



It is estimated that a follovving mnd of 10 knots will blow 

 over the entire distance of decay. The computation of the wave 

 height at the end of the distance of decay, H^ -g, , is carried out 

 as follows, using the symbols in Table VI: 



48 



