±i± uscuiii, 



VOL. XXVII. , FEBEUAKY, 1909. 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



\ 



Editor: EDWAKD S. DANA. 



ASSOCIATE EDITORS 



Professors GEOKGE L. GOODALE, JOHN TKOWBKIDGE, 

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



Professors ADDISON E. VEERILL, HORACE L. WELLS, 

 L. Y. PIRSSON and H. E. GREGORY, of New Haven, 



Professor GEORGE F. BARKER, of Philadelphia, 



Professor HENRY S. WILLIAMS, of Ithaca, 

 Professor JOSEPH S. AMES, of Baltimore, 

 Mr. J. S. DILLER, of Washington. 



FOURTH SERIES 



No. 158— FEBRUARY, 1909. 

 YOL. XX VII— [WHOLE NUMBER, CLXXVIL] 



WITH PLATES II-IV. 



NEW HAVEN, CONNECTICUT. 



1909. 



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



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Published monthly. Six dollars per year, in advance. $6.40 to countries in the 

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