\H 



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 Ithaoa, 



Professor JOSEPH S. AMES, of Baltimore, 



Mr. J. S. DILLER, of Washington. 



FOURTH SERIES 

 VOL. XLII— [WHOLE NUMBER, CXCII]. 



WITH PLATE I. 



NEW HAVEN, CONNECTICUT 



1916. 



