i^'- VOLUME XXVII 



,^^|^g5>i^^ 



LeRARY 



NUMBER I 



Journal of Geology 



A Semi-Quarterly 



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. EDGE WORTH DAVID, Australia 



BAILEY WILLIS, Leland Stanford Junior University 



CHARLES D. WALCOTT, Smithsoniau Institution 



JOSEPH P. IDDINGS, Washington, D.C. 



JOHN C. BRANNEli, Leland Stanford Junior University 

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

 WILLIAM H. HOBBS, University of Michigan 

 FRANK D. ADAMS. McGill University 

 CIL.RLK.'^ K. LEITH, University of Wisconsin 

 WALLACE W. ATWOOD, Harvard University 

 WILLIAM H. EMMONS, University of Minnesota 

 ARTHUR L. DAY. Carnegie Institution 



JANUARY-FEBRUARY 1920 



DL\STROPHISM AND THE FORMATIVE PROCESSES. X. THE ORDER OF MAGNI- 

 TUDE OF THE SHRINKAGE OF THE EARTH DEDUCED FROM MARS, VENUS, 

 AND THE MOON . - - . T. C. Chamberlix i 



THE LAWS OF ELASTICO-VISCOUS FLOW. II - - - - - A. A. Michelson i8 



THE GREAT GLASS-SPONGE COLONIES OF THE DEVONIAN; THEIR ORIGIN, RISE, 



AND DISAPPEARANCE .--.---.. John M. Cl.arke 25 



A QUANTITATIVE MINER.\LOGICAL CLASSIFICATION OF IGNEOUS 



ROCKS— REVISED. PARTI Albert Joh.wxsen 38 



THE PRE-MOENKOPI (PRE-PERMIAN ?) UNCONFORMITY OF THE COLORADO 



PLATEAU ------- C. L. D.ake 61 



P.VLEOZOIC DIASTROPHICS of THE NORTHERN MEXICAN 



TABLELAND Charles Ke\U 75 



SOME ESTIMATES OF THE THICKNESS OF THE SEDIMENTARY ROCKS 



OF OHIO - - - - - - . - - T. M. Hills 84 



RECENT PUBLICATIONS - - . . . . S7 



THE UNIVERSITY OF CHICAGO PRESS 



CHICAGO,* ILLINOIS, U.S.A. 



THE CAMBRIDGE UNIVERSITY PRESS, London 



THE MARUZEN-KABUSHIKI-KAISHA, Tokyo, Osaka. Kyoto. Fukdoka Sendai 



THE MISSION BOOK COMPANY, Shanghai 



