

THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA. 



ASSOCIATE EDITOES 



Professors GEORGE L. GOODALE, JOHN TROWBRIDGE, 

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



Professors ADDISON E. VERRILL, HORACE L. WELLS, 

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



Professor HENRY S. WILLIAMS, of Ithaca, 

 Professor JOSEPH S. AMES, of Baltimore, 

 Mr. J. S. DILLER, of Washington. 



FOURTH SERIES 



VOL. XXXII-[WHOLE NUMBER, CLXXXIL] 



• No. 3 90-OCTOBER, 1911.^^ 



MARlSlvi 



NEW HAVEN, CONNECTICUT^ ft 



Wonal Mug JjX 



1911 



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