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 JULY-AUGUST, 1912 ‘No.5 
THE EVIDENCE OF THREE DISTINCT GLACIAL EPOCHS 1N THE PLEISTOCENE HISTORY OF THE 
SAN JUAN MOUNTAINS, COLORADO - - - - Wattace W. Atwoop AND Kirtley F. MATHER 385 
THE OLD EROSION SURFACE IN IDAHO: A CRITICISM - - - = - - ELIor BLACKWELDER ais 
GLACIATION OF THE ALASKA RANGE - - - - - - - - - - STEPHEN R. Capps 415 
SOME SMALL NATURAL BRIDGES IN EASTERN WYOMING - -- - - -  -~ V. 4H. Barnerr 438 
ROCK-CUD SURFACES IN > THE DESERT (RANGES aici to) cla i kui SIDNEY PaIcE 442 
SPECULATIONS REGARDING THE GENESIS OF THE DIAMOND. 10 = > -«- Orvitte A. DERBY 451, 
THE ORDER OF CRYSTALLIZATION IN IGNEOUS ROCKS- - §- - - - - N. L. BowEN 457 
PETROLOGICAL ABSTRACTS AND REVIEWS Se Ee Nias Cea I sy ma tant SNe DS cned ee et A OG) 
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