Library, U. S. Nat. Museum. 



VOL. XLIY. 



DECEMBER, 1917, 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWAKD S. DANA. 



ASSOCI iTE EDITORS 



Professors GEORGE L. GOOD ALE, JOHN TROWBRn)GB, 

 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. XLIY— [WHOLE NUMBER, CXCIY] 

 No. 264— DECEMBER, 1917. 



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^ DEC 



1917. 



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