various nonlinear solutions. Modulations, group velocities, instabil- 

 ities, averaging methods, and solutions are all described in adequate 

 detail . 



Coastal Engineering Significance. The book is a definitive account of 

 recent work to which the author is one of the more important 

 contributors. In 1981 it is still a valuable up-to-date textbook and 

 reference for the basic theory of wave propagation. 



61 



