57?6.75 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWAED S. DANA. 



ASSOCIATE EDITORS 



Professors GEOKGE L. GOODALE, JOHN TEOWBEIDGE, 

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



Professors ADDISON E. VEEEILL, HOEACE L. WELLS, 

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



Professor GEOEGE E. BAEKEE, of Philadelphia, 

 Professor HENEY S. WILLIAMS, of Ithaca, 

 Professor JOSEPH S. AMES, of Baltimore, 

 Mr. J. S. DILLEE, of Washington. 



FOURTH SERIES 

 VOL. XXVI— [WHOLE NUMBEE, CLXXVL] 



NEW HAVEN, CONNECTICUT. 



1 908 



Z,o 



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