MH 



THE 



JOURNAL OF GEOLOGY 



A Semi-Quarterly Magazine of Geology and 

 Related Sciences 



EDITED BY 

 THOMAS C. CHAMBERLIN AND ROLLIN D. SALISBURY 



With the Active Collaboration of 



STUART WELLER, 



Invertebrate 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 



T. W. EDGEWORTH DAVID, Australia 



BAILEY WILLIS, Leland Stanford Junior 



Univerisity 

 CHARLES D. WALCOTT, Smithsonian 



Institution 



JOSEPH P. IDDINGS, Washington, D.C. 

 JOHN C. BRANNER, Leland Stanford Junior Uni- 

 versity 

 RICHARD A. F. PENROSE, Jr., Philadelphia, Pa. 

 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 XXVIII 

 JANUARY-DECEMBER, 1920 



THE UNIVERSITY OF CHICAGO PRESS 

 CHICAGO, ILLINOIS 



