VOL. XXVII. 



JUNE, 1909. 



Established by BENJAMIN SILIIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE 



Editor: EDWAED S. DANA. 



ASSOCIATE EDITORS 



Professors GEOKGE L. GOODALE, JOHN TROWBRIDGE, 

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



Professors ADDISON E. VERRILL, HOKACE L. WELLS, 

 L. V. PIKSSON and H. E. GKEGOKY, of New Haven, 



Professor GEOKGE F. BARKER, of Philadelphia, 

 Professor HENRY S. WILLIAMS, of Ithaca, 

 Professor JOSEPH S. AMES, of Baltimore, 

 Mr. J. S. DILLER, of Washington; 



FOURTH SERIES 



VOL. XXYII-[WHOLE NUMBER, CLXXVIL1 

 No. 162— JUNE, 1909. 



NEW HAVEN, CONNECTICUT. 



1909. 



THE TUTTLE, MOREHOUSE & TAYLOR CO., PRINTERS, 123 TEMPLE STREET. 



Published monthly. Six dollars per year, in advance. $6.40 f " "flnntirinn in, the 

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( JUN 1 1909 



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