Charles D. Waicott, 



Of fice Geological Survey. 



No. 186. Vol. XXXI. , JUNE, 1886. 



Established by BENJAMIN SILLIMAN in 1818. 



THE 



AMERICAN 



JOURNAL OF SCIENCE. 



EDITORS 



JAMES D. and EDWARD S. DANA. 



ASSOCIATE EDITORS 



Professors ASA GRAY, JOSIAH P. COOKE, and 

 JOHN TROWBRIDGE, of Cambridge, 



Professors H. A. NEWTON and A. E. YERRILL, of 

 New Haven, 



Professor GEORGE F. BARKER, of Philadelphia. 



THIRD SERIES. 



VOL. XXXI. -[WHOLE NUMBER, CXXXI.J 



No. 186— JUNE, 1886. 



WITH PLATE X. 



NEW HAVEN, CONN. : J. D. & E. S. DANA. 

 1886. 



TUTTLE, MOREHOUSE & TAYLOR, PRINTERS, 371 STATE STREET. 



Six dollars per year (postage prepaid). $6.40 to foreign subscribers of countries in 

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

 letters, or bank checks. 



