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This is a reissue in the Cambridge Mathematical Library series of a book first published in 1978. When it was first issued, it had enormous impact on all those working in fluid flows, and on waves in particular. I quote from the review by D C Pack, published in 1979 in the Journal of Fluid Mechanics (vol 90, pp 605-8): ``The book will become a standard work for reading and consultation by all interested in fluid flow. It will be invaluable to research students ... Even among the most experienced readers few, if any, will fail to find in it new insights ... comments and comparisons that illuminate the chapters.'' The same comments can be made today, because in spite of the two and a half decades that have now passed, it retains its immediacy and vitality.
James Lighthill (Wed,) studied this question.