Acknowledgements 
The author wishes to express his sincere thanks to the 
many people who have helped in the preparation of this work. 
The list is long, and it consists of many persons from many 
organizations from all over the United States. 
At New York University, there are those who were and are 
on the immediate staff of the project. Mr. D. P. Martineau, now 
of Woods Hole and ifr. Richard James, now of A. H. Glenn and 
Associates, helped in the early part of this work. Mr. Wilbur 
Marks, Mr. Tony Isnardi, and Mr. John Woolley helped to prepare 
this book. Professor Bernhard Haurwitz, director of the Beach 
Erosion Board project, helped by critical discussion and by 
suggested improvements of the final draft. Professor Hans A. 
Panofsky, now of Pennsylvania State College, helped in many early 
stimulating discussions of power spectra. 
At the Institute for Mathematics and Mechanics of New York 
University, Professor Joseph B. Keller and Professor Eugene 
Isaacson helped me in discussions of some of the mathematical 
details involved. 
In addition at New York University, there are those on the 
regular University staff who helped in the preparation of this 
work. My thanks are due to Mrs. Sadelle Wladaver who typed the 
text and Mr. Gerhard Reinert and Mr. Arthur Klein who drafted the 
many plates and figures. 
At the Office of Naval Research, I wish to express my 
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