BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 31, pp. 177-184 March 31, 1920 



PKOCEEDIXGS OF THE FIFTEENTH SUMMER MEETING, 

 HELD IN CONJUNCTION WITH THE SIXTEENTH AN- 

 NUAL MEETING OF THE CORDILLERAN SECTION, UNI- 

 VERSITY OF CALIFORNIA AND STANFORD UNIVERSITY, 

 AUGUST 3, 4, AND 5, 1915. 



J. A. Taff, Secretary 



CONTENTS 



Page 

 Session of Tuesday, August 3 178 



Epigeue profiles of the desert [discussion] ; by Andrew C. Lawson... 178 



The bajadas of the Santa Catalina Mountains, Arizona [discussion] ; 

 by C. F. Tolmau, Jr 178 



Origin of the Tufas of Lake Lahontan ; by J. C. Jones 179 



Some physiographic features of bolsons [title] ; by H. E. Gregory 179 



Sculpturing of rock by winds in the Colorado Plateau Province [dis- 

 cussion] ; by H. E. Gregory 179 



Session of Wednesday, August 4 180 



Some chemical factors affecting secondary sulphide ore enrichment 

 [discussion] ; by S. W. Youjig 180 



Role of colloidal migration in ore deposits [discussion] ; by John D. 

 Clarke 180 



Some examples of progressive changes in the mineral composition of 

 copper ores [discussion] ; by C. F. Tolman, Jr 180 



Sericite. a low-temperature hydrothermal mineral; by A. F. Rogers.. 180 



Annual dinner 181 



Ses.sion of Thursday, August 5 181 



Physiographic control in the Philippines [discussion] ; by Warren D. 

 ^mith 181 



Origin of the basins within the Hamada of the Libyan Desert [title] ; 

 by William H. Hobbs I81 



The limited effective vertical range of the desert sand-blast, based 

 on observations made in the Libyan Desert and in the Anglo-Egyp- 

 tian Sudan [title] ; by William H. Hobbs 181 



Diastrophism of the Pacific coast [title] ; by R. S. Holway 181 



Notes on Mount Lassen eruptions [title] ; by .T. S. Diller 181 



Geology of portions of western Washington [discussion] ; by Charles 

 E. Weaver '. Ig2 



The problem of the Texas Tertiary sands [discussion] ; by E. T. 

 Durable 182 



Pisolites at San Antonio. Texas [discussion] ; by Alexander Deussen. 182 

 XII — Bull. Geol. Sor. A.m.. Vol. :n, V.)V.) (177) 



