VOL. XL. AUGUST, 1915. 



Established by BENJAMIN SILIIMAN in 1818. 



THE 



AMERICA 



JOURNAL OF SCIENCE. 



Editor: EDWAED S. DANA. 



ASSOCIATE EDITORS 



Professors GEOKGE L. GOODALE, JOHN TEOWBETDGE, 

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



Professors ADDISON E. VEREILL,. HOEACE L. WELLS, 



LOUIS V. PIESSON, HEEBEET E. GEEGOET 



and HOEACE S. UHLEE, of New Haven, 



Professor HENRY S. WILLIAMS, of Ithaca, 



Professor JOSEPH S. AMES, of Baltimore, 



Mr. J. S. DILLEE, of Washington. 



FOURTH SERIES 



VOL. XL— [WHOLE OTMBEE, CXCJ. 

 No. 236— AUGUST, 1915. 



NEW HAVEN, CONNECTICUT. 



1915. 



THE TUTTLE, MOREHOUSE & TAYLOR CO., PRINTERS, 123 TEMPLE STREET. 



Published monthly. Six dollars per year, in advance. $6.40 to countries in the 

 Postal Union ; $6.25 to Canada. Eemittances should be made either by money orders, 

 registered letters, or bank checks (preferably on New York banks). 



