VOLUME 2 
APRIL, 1916 
NUMBER 4 
PROCEEDINGS 
OF THE 
National Academy 
OF Sciences 
OF THE 
UNITED STATES OF AMERICA 
EDITORIAL BOARD 
Arthur A. Noyes, Chairman 
Arthur L. Day, Home Secretary 
Edwin B. Wilson, Managing Editor 
George E. Hale, Foreign Secretary 
J. J. Abel 
W. B. Cannon 
J. McK. Cattell 
J. M. Clarke 
E. G. CONKLIN 
J. M. Coulter 
C. B. Davenport 
Simon Flexner 
E. B. Frost 
R. G. Harrison 
W. H. Holmes 
J. P. Iddings 
R. A. Millikan 
E. H. Moore 
Alexander Smith 
Publication Office: Williams & Wilkins Company, Baltimore 
Editorial Office: Massachusetts Institute of Technology, Boston 
Home Office of the Academy: W^ashington, D. C. 
Entered as second-dass matter at the Post Office at Baltimore, Md., under the Act of August 24, 1912 
