

"•A* 



VOL. XXXIX. JUNE, 1915. 



i 



Established by BENJAMIN SILLIMAN in 1818. 



THE . I AUG § 1915 



AMERICA 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA. 



ASSOCIATE EDITOES 



Professors GEORGE L. GOODALE, JOHN TROWBRIDGE, 

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



Professors ADDISON E. YERRILL, 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. XXXIX— [WHOLE NUMBER, CLXXXIX], 

 No. 234— JUNE, 1915. 



WITH PLATE IX. 



NEW HAVEN, CONNECTICUT. 



19 15. 



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