NH 



THE 



JOURNAL OF GEOLOGY 



A Semi-Quarterly Magazine of Geology and 

 Related Sciences 



EDITORS 

 Thomas C. Chamberlin, in General Charge; Rollin D. Salisbury, Geographic Geology; 

 Samuel W. Williston, Vertebrate Paleontology; Stuart Weller, htvertebrate Paleontology: 

 Albert Johannsen, Petrology; Rollin T. Chamberlin, Dynamic Geology, 



ASSOCIATE EDITORS 

 Sir Archibald Geikie, Great Britain; Charles Barrois, France; Albrecht Penck, 

 Germany; Hans Reusch, Norway; Gerard DeGeer, Sweden; Orville A. Derby, Brazil; 

 T. W. Edgeworth David, Australia; Bailey Willis, Argentina; Grove K, Gilbert, 

 Washington, D.C.; Charles D. Walcott, Smithsonian Institution; Henry S. Williams, Cor- 

 nell University; Joseph P. Iddings, Washington, D.C.; John C. Branner, Leland Stanford 

 Junior University ; Richard A. F. Penrose, Jr., Philadelphia, Pa.; William B. Clark, Johns 

 Hopkins University; William H, Hobbs, University of Michigan; Frank D, Adams, McGill 

 University; Charles K. Leith, University of Wisconsin; Wallace W. Atwood, Harvard 

 University; William H, Emmons, University of Minnesota; Arthur L. Day, Carnegie 

 Institution. 



VOLUME XXIII 



JANUARY-DECEMBER, 1915 



THE UNIVERSITY OF CHICAGO PRESS 

 CHICAGO, ILLINOIS 



