VOL. XVIII. DECEMBER, 1904. 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors GEORGE L. GOODALE, JOHN TROWBRIDGE, 

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



Professors ADDISON E. VERRILL, HORACE L. WELLS, 

 L. V. 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. 



VOL.- XVIII— [WHOLE NUMBER, CLXVIIL] 



No. 108.— DECEMBER, 1904. 



WITH PLATE XX. 



NEW HAVEN, CONNECTICUT. 

 1904 



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Published monthly. Six dollars per year, in advance. $6.40 Wcou^iV|ifes in the 

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