5 o^ 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWAED S. DANA. 



ASSOCIATE EDITORS 



Professors GEOKGE L. GOODALE, JOHN TKOWBKTDGE, 

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



Professors ADDISON E. VEKKILL, HORACE L. WELLS, 

 L. V. PIESSON 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 



VOL. XXVIII— [WHOLE NUMBER, CLXXVIII.] 



WITH TWO PLATES. 



NEW HAVEN, CONNECTICUT. 



1909. 



%o(\%A^ 



