VOL. XIX. 



APRIL, 1905. 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



Editor: EDWARD S. DANA 



ASSOCIATE EDITORS 



Professors GEOKGE L. GOOD ALE, JOHN TROWBRIDGE, 

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



Professors ADDISON E. VERRILL, HORACE L. WELLS, 

 L. V. PIRSSON and H. E. GREGORY, of New Haven, 



Professor GEORGE E. BARKER, of Philadelphia, 

 Professor HENRY S. WILLIAMS, of Ithaca, 

 Professor JOSEPH S. AMES, of Baltimore, 

 Mr. J. S. DILLER, of Washington. 



FOURT H SERIES. 

 YOL. XIX— [WHOLE NUMBER, CLXIX.] 



No. 112.— APRIL, 1905. 



WITH PLATE II. 



NEW HAVEN, CONNECTIC 

 1905 



THE TTJTTLE, MOREHOUSE & TAYLOR CO., PRINTERS, 1 



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

 Postal Union. Remittances should be made either by money orders, registered 

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



