VOL. XXXII. DECEMBER, L911. 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors GEOKGE L. QOODALE, JOHN TROWBRLDGE, 

 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. 192— DECEMBER, 1911. 



NEW HAVEN, CONNECTICUT. 



1911. fa,. 



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