The Fournal of Geology 
Published on or about the following dates: February 1, March 15, May 1, June 15, 
August 1, September 15, November 1, December 15. 
Vol. XX CONTENTS FOR SEPTEMBER-OCTOBER, 1912 No. 6 
MICROSCOPICAL PETROGRAPHY FROM THE QUANTITATIVE VIEWPOINT - _ Frep. EUGENE WRIGHT 481 
GLACIATION IN THE TELLURIDE QUADRANGLE, COLORADO - = - = = ALLEN Davin Hote 502 
ON THE STRATIGRAPHIC POSITION AND AGE OF THE JUDITH RIVER FORMATION - _ A.C. PEaLE 530 
MODIFICATIONS OF THE QUANTITATIVE SYSTEM OF CLASSIFICATION OF IGNEOUS ROCKS 
Wurman Cross, J. P. Ippines, L. V. Pirsson, H. S. WASHINGTON 550 
ISOSTASY, A REJOINDER TO THE ARTICLE BY HARMON LEWIS See ee OPS Joun-F. Havrorn' | / 562" 
REVIEWS (iden Raney Sing SC Arty ere eesti Nye US aig cig PR ee ed ae 
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