VOL. XXXV. MARCH, 1913. 



Established by BENJAMIN SIILIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE 



Editor: EDWAKD S. DANA. 



ASSOCIATE EDITORS 



Professors GEORGE L. GOODALE, JOHN TROWBRIDGE, 

 W. G. FARLOW and WM. M. DAVIS, of Cambridge, 



Professors ADDISON E. VERRILL, HORACE L. WELLS, 



LOUIS V. PIRSSON, HERBERT E. GREGORY 



and HORACE S. UHLER, of New Haven, 



Professor HENRY S. WILLIAMS, of Ithaca, 



Professor JOSEPH S. AMES, of Baltimore, 



Mr. J. S. DILLER, of Washington. 



FOURTH SERIES 



VOL. XXXY— [WHOLE NUMBER, CLXXXV], 



No. 207— MARCH, 1913. 



S^onian lnst/'t 7 

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NOV 14 1913 



NEW HAVEN, CONNECTICUT. 

 1913. 



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