The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
NATIONAL ACADEMY PRESS • 2101 Constitution Avenue, N.W. • Washington, D.C. 20418
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 competences and with regard for appropriate balance.
This study was supported by grants from Mitchell Energy and Development Corporation, the George and Cynthia Mitchell Foundation, and the National Research Council. Additional support for the Summer Study, 1996 was provided by Contract No. 56-DKNA-5-31000 between the National Academy of Sciences and the National Oceanic and Atmospheric Administration. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the organizations or agencies that provided support for the project.
Additional copies of this report are available from the National Academy Press, 2101 Constitution Avenue, N.W., Lockbox 285, Washington, D.C. 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); http://www.nap.edu
Library of Congress Catalog Card Number 99-50619
International Standard Book Number 0-309-06783-9
Printed on Recycled Paper
Copyright 1999 by the National Academy of Sciences. All rights reserved.
Printed in the United States of America