f"^ 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWAED S. DANA. 



ASSOCIATE EDITORS 



Professors GEORGE L. GOODALE, JOHN TEOWBRIDGE, 

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



Professors ADDISON E. VEREILL, HORACE L. WELLS, 

 L. V. PIESSON and H. E. GEEGOET, op New Haven, 



Professor HENEY S. WILLIAMS, of Ithaca, 

 Professor JOSEPH S. AMES, of Baltimore, 

 Mr. J. S. DILLEE, op Washington. 



FOURTH SERIES 

 VOL. XXX-[WHOLE NUMBER, CLXXX.] 



WITH TWO PLATES. 



NEW HAVEN, CONNECTICUT. 



1910. 



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