yj . vj. X-03.L. uiuscuiii 



VOL. XXVII. MAY, 1909. 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWAED S. DANA. 



ASSOCIATE EDITORS 



Professors GEOKGE L. GOODALE, JOHN TEOWBELDGE, 

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



Professors ADDISON E. VEEEILL, HOEAOE L. WELLS, 

 L. V. PIESSON and H. E. GEEGOEY, of New Haven,- 



Professor GEOEGE F. BAEKEE, of Philadelphia, 

 Professor HENEY S. WILLIAMS, of Ithaca, 

 Professor JOSEPH S. AMES, of Baltimore, 

 Mr. J. S. DILLEE, of Washington. 



FOURTH SERIES 



No. 161— MAY, 1909. 



VOL. XXVII— [WHOLE NUMBER, CLXXVIL] 



NEW HAVEN, CONNECTICUT. 

 1909. 



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