

THE 



AMERICAN" 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA 



ASSOCIATE EDITORS 



Professors GEORGE L. GOODALE, JOHN TROWBRIDGE, 

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



Professors ADDISON E. VERRILL, HORACE L. WELLS, 



LOUIS V. PIRSSON, HERBERT E. GREGORY 



and HORACE S. UHLER, of New Haven, 



Professor HENRY S. WILLIAMS, of Ithaca, 



Professor JOSEPH S. AMES, of Baltimore, 



Mr. J. S. DILLER, of Washington. 



FOURTH SERIES 



VOL. XL.— [WHOLE NUMBER, CXC.] 



WITH THREE PLATES. 



NEW HAVEN, CONNECTICUT. 



1915. 



a,Vi&5<b 



