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VOLUME 7 NOVEMBER, 1921 NUMBER 11 
PROCEEDINGS 
OF THE 
National Academy 
of Sciences 
OF THE 
UNITED STATES OF AMERICA 
EXECUTIVE COMMITTEE 
Edwin Bid well Wilson, Managing Editor 
Raymond Pearl Vernon Kellogg 
PUBLISHED MONTHLY g 
Publication Office : Eschenbach Printing Company, Easton, Pa. 1 
Editorial Office: Massachusetts Institute of Technology, Cambridge 
Home Office of the Academy: Washington, D. C. 1 
£5 == 
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Entered as second-class matter June 21, 1920, at the postomce at Easton, Pennsylvania, under the act of August 24, 1912. 
Acceptance for mailing at special rate of postage provided for^n section 1103, Act of October 3, 1917. Authorized June 18, 1920. 
