FOREWORD 
It is great honor to me to be invited to give the first 
in the series of David W. Taylor Lectures. My associations 
with the Model Basin date from a long time ago, and a visit 
to the United States is for me not a real visit unless I 
have the opportunity to taste once more the stimulating 
atmosphere which not only gives the Model Basin an out 
standing place in hydrodynamical research but also acts as 
a breeding ground where nearly all outstanding people in the 
field passed an essential period in their lives. So I am 
extremely grateful to have been given the opportunity once 
more to spend some time at this most interesting place and 
to participate in its work. I wish to express my gratitude 
to Justin McCarthy who originated the idea of the lectures 
and to all other friends who made this period a success. 
In particular, I am pleased that Dr. Langan, whom I used to 
know as a promising undergraduate student, did a fine job 
in editing the lectures. 
R. TIMMAN 
