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VOLUME 7 AUGUST, 1921 NUMBER S 
| PROCEEDINGS | 
i 
I OF THE 
I National Academy 
I of Sciences 
j OF THE 
I UNITED STATES OF AMERICA 
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I . I' 
1 EXECUTIVE COMMITTEE 
1 Edwin Bidwell Wilson, Managing Editor 
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i Raymond Pearl Vernon Kellogg , m 
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I PUBLISHED MONTHLY j 
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1 Publication Office: Eschenbach Printing Company, Easton, Pa. 1 
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| Editorial Office: Massachusetts Institute of Technology, Cambridge 
| Home Office of the Academy: Washington, D. C. 1 
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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. Authorised June 18, 1920. 
Price per annum. I5J00 
