NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competencies and with regard for appropriate balance.

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 Sciences, the National Academy of Engineering, and the Institute of Medicine.

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 reflect the views of the sponsor.

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.