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1 I 
VOLUME 7 JUNE, 1921 NUMBER 0 
PROCEEDINGS 
OF THE 
National Academy 
I of Sciences 
OF THE 
UNITED SfATES OF AMERICA 
i 
I 
1 EXECUTIVE COMMITTEE 
Edwin Bidweix WitsoN, Managing Editor 
Raymond Pearl Vernon Kellogg 
I P UBLISHED MONTHL Y 
I 
| Publication Office: Eschenbach Printing Company, Easton, Pa. 
| Editorial Office: Massachusetts Institute of Technology, Cambridge 
I 
Home Office of the Academy: Washington, D. C. 
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Entered as second-class matter June 21, 1920, at the postoffice at Easton, Pennsylvania, under the act of August 24, 1912- 
Acceptance for mailing at special rate of postage provided for in section 1103, Act of October 3, 1917. Authorized June 18, 1920. 
Price per annum, $5.00 
