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This report has been reviewed by a group other than the authors according to procedures 

 approved by a Report Review Committee consisting of members of the National Academy of Sci- 

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This report and the committee were supported by a contract with the Office of Naval Research, 

 Department of the Navy, The views expressed herein are those of the authors and do not necessarily 

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Cover art by Carrie Mallory. Ms. Mallory received her Bachelor of Fine Arts degree from 

 Cooper Union. She draws on the natural world and the effects of age on man-made objects for many 

 of her themes. She has exhibited at a number of juried shows in the Northern Virginia area. The art 

 for this cover was inspired by a pile of rusting objects in a shipyard at Lunenberg, Nova Scotia. 



Copies of this report are available from Ocean Studies Board, National Research Council, 2101 

 Constitution Avenue, N.W., Washington, D.C. 20418. 



Copyright 1996 by the National Academy of Sciences. All rights reserved. 



Printed in the United States of America. 



