hydrographic engineers MM. Gougenheim. and Lacombe, to M. de
Rouville, Inspector General of Lighthouses and Buoys, to Professor
Fairbridge of Columbia University, and to all others who have helped.

As the French edition of this book appeared in 1954, modifications
and additions have been made here in the text and in bibliographies.
I have been helped by the criticisms of Professors Baulig and Musset,
and I have incorporated the results of some recent advances in know-
ledge, so that this is really a new edition and not merely a translation.
Many thanks are due to Professor Steers, the originator of the English
edition, and to Mr Sparks and the Rev. Kneese, who have prepared
the translation.

A. G.

October 1957

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