Ocean Wave Spectra and Shtp Appltcattons 
of the angle incidence spacial repartition of the energy from the 
main direction, and the concept of the superposition of different uni- 
directional spectra coming from different directions. 
DISCUSSION 
Manley Saint-Denis 
Untverstty of Hawat 
Honolulu, U.S.A. 
The spectral theory of waves is a difficult subject to discuss 
with clarity and cohesion because the subject, even today, is in great 
turmoil and no matter how much or how well is said about it, even 
more remains in doubt. At the present state of the art, a point can 
be strongly developed only by disregarding a plethora of other points 
which, however, remain to haunt one like ghosts demanding to be 
heard in the night. 
Miss Chang's Paper is a welcome and well-written exposition 
on a point of keen interest, namely, do the idealisations made in the 
effort to obtain a working description of the sea yield disfigurations 
of reality ? Miss Chang believes that the correspondence between 
model and reality is unsatisfactory, yet I suspect this is only a ques- 
tion of standards and that hers are somewhat higher than those of us 
who, being older, have learnt that nature, no matter how well-behav- 
ed, cannot be very well fitted by simple formulae, no matter how well 
they may be conceived. For me, the fit of measured and idealised 
spectra in Figure 5 of the text seems to be very good. 
Miss Chang suspects the usefulness of the two-parameter 
spectrum and suggests a data bank. Such an idea would have been 
frightening a few years ago but now that computers with abundant 
memory are available, the suggested solution is feasible, yet for all 
the merit of the idea I should like to enter a plea for elegance - that 
is, for minimum effort, that is, for simple formulations instead of 
quasi-infinities of numbers, the designer will be happier ; for, having 
been brought up over the past century to depend ona length over 20 
wave, he would appreciate something almost quite so simple. Whether 
the simple formula can be fitted to the vagaries of the sea wave de- 
pends, in my opinion, on how representative the probability distri- 
butions of Figures 2 and 4 in the text are, i.e. upon whether the 
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