ABSTRiVCTS AND DISCUSSIONS OF PAPERS 395 



of the Bonanza Mine, Alaska; two-colored chalcocite; meta-colloidal chalcoeite, 

 and the use of the terms primary and secondary as applied to minerals. 



Presented in full extemporaneously. 



Discussion 



Prof. A. C. Lawson questioned the propriety of such definite conclusions on 

 interpretations from examinations of ore sections. 



8ERICITE, A LOW TEMPERATURE HYDROTHERMAL MINERAL 



BY A. F. ROGERS ' 



(Abstract) 



Microscopic study of ores of various types indicate that sericite is a rather 

 low-temperature mineral formed at or toward the close of the hydrothermal 

 period. Few, if any, of the hypogene minerals are later than sericite. Sericite 

 not only replaces quartz and the silicates, but also various sulphides and 

 sulpho-salts, such as pyrite, chalcopyrite, bornite, chalcoeite, etcetera. The 

 sericite of metamorphic rocks is also formed at a late stage. 



Presented in full extemporaneously. Discussion was deferred. 



DINNER 



A joint dinner of the Geological, Paleontological, and Seismological 

 Societies was held at the Engineers' Club, at 7.30 o'clock p. m., about 50 

 persons participating. 



Session of Thursday, August 5 



The Society convened at 10.15 o'clock a. m., in Bacon Hall, University 

 of California, Dr. C. P. Tolniau, Jr., in the chair and J. A. Taff acting 

 as Secretary. 



TITLES AND ABSTRACTS OF PAPERS PRESENTED AND DISCUSSIONS THEREON 



I'llYSIOOh'APIIIC CONTROL IN THE PHILIPPINES 



BY WARREN D. SMITH 



{Ahsiract) 



The autlinr i)i-i'sciitc(| m [■Osuiiie of I'liiliiipine geology and tlie resulting 

 physiographic sectois and a consideration of their effect on the distribution. 



* Introduced by C. F. Tolinun, .Ir. 



