This has been a most interesting Discussion to attend, and will, I believe, in its written version, be a work of marked permanent value, especially because the contributors, as well as giving penetrating and comprehensive reviews of their own parts of the subject, have carefully elucidated also the relations between the parts. Methods apparently of very diverse character for analysing the nonlinear development of dispersive waves have been described. Although they have different areas of validity, there are regions of overlap between those areas, where contributors have taken pains to show that they give identical results. In particular, the relations between Whitham’s variational method, Brooke Benjamin’s stability analyses, the mode interaction techniques of Phillips and Longuet-Higgins, and Hasselmann’s work on random wave fields, have become much clearer, so that the advances of the past six years begin to form a coherent pattern. Some uncertainties, and many unsolved problems, remain; but comparisons of the existing theories with experiment have yielded such encouraging results, that many workers are likely to attempt further developments of them in the near future.
