CONTENTS OF VOLUME XX] 
NUMBER I 
THE SECONDARY ENRICHMENT OF SILVER ORES. H. C. Cooke 
THE GEOLOGY OF Luzon, P.I. Warren D. Smith, Ph.D. 
PRELIMINARY NOTES ON SOME IGNEOUS Rocks oF JAPAN. S. Kozu 
THe QuizzyHota Laccouitr. E. H. L. Schwarz . 
AN AccEssoRY LENS FOR OBSERVING INTERFERENCE FIGURES OF 
SMALL MINERAL Grains. Albert Johannsen 
REVIEWS 
NUMBER II 
THE RELATIVE SOLUBILITIES OF THE CHEMICAL CONSTITUENTS OF 
ROCKS. | C3; H. Smyth; Jr: . 3 ; : ' 
THE COBALT SERIES; ITS CHARACTER AND ORIGIN. Morley E. Wilson 
THE LATER CENOZzOIC HISTORY OF THE WIND RIVER MOovunrtTAINS, 
Wyominc. Lewis G. Westgate and E. B. Branson 
VARIATIONS OF CERTAIN ADIRONDACK Basic IntRusIvES. William J. 
Miller 
“THE ORDER OF CRYSTALLIZATION IN IGNEOUS Rocks.” Victor 
Ziegler 
ANGISTORHINUS, A NEW GENUS OF PHYTOSAURIA FROM THE TRIAS 
oF Wyominc. Maurice G. Mehl 
REVIEWS 
NUMBER III 
CHEMICAL COMPOSITION AS A CRITERION IN IDENTIFYING META- 
MORPHOSED SEDIMENTS. Edson S. Bastin 
OBSERVATIONS ON THE FELDSPARS. Austin F. Rogers 
Rock CLASSIFICATION ON THREE (CO-ORDINATES. Alexander N. 
Winchell 
THE OLD EROSION SURFACE IN IDAHO. Joseph B. Umpleby 
NOTES ON THE ORIGIN OF CERTAIN PALEOZOIC SEDIMENTS, ILLUSTRATED 
BY THE CAMBRIAN AND ORDOVICIAN ROCKS OF CENTER COUNTY, 
PENNSYLVANIA. Thomas C. Brown 
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