nized. Even for those closely associated with the subject, it has been difficult to keep track of developments over the years. This book is therefore of particular value in that it collects together 40 relevant scientific papers based on the low-frequency attenuation program carried out by the Naval Underwater Systems Center over the past 20 years. The collation of these key papers in one cover not only emphasizes afresh the contribution made by NUSC to this branch of underwater acoustics, but aids in the appreciation of the historical development of the subject. The book is an appropriate companion to the earlier publication, which collects together the NUSC technical reports, documents, and general memoranda dealing with all aspects of the same program. It should be of equal interest and value to those associated with the field. As with previous issues in the series of collections documenting the Center's contributions in scientific fields, copies are available from NUSC.
A. C. KIBBLEWHITE
University of •4ucklandNew Zealand too elementary in parts. If it is for the nonseismologist, then, in many instances, the explanations of terminology and the discussions of many of the illustrations are inadequate. The illustrations themselves are generally of good quality; however, there are a few notable exceptions, in Chap. 6 where in two instances the reproduction is poor and in Chap. 2 where the trace sections do not appear to illustrate the point that the text claims they illustrate. Despite these shortcomings, the book should provide a reader, familiar with seismology but unfamiliar with pulse coding techniques, a concise overview of the techniques currently being used.
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