TITLES AND ABSTRACTS OF PAPERS 43 



TITLES AND ABSTRACTS OF PAPERS PRESENTED BEFORE THE THIRD SECTION 

 AND DISCUSSIONS THEREON 



The third section convened about 2.30 o'clock p. m., with Yioe-Presi- 

 dent James F. Kemp serving as chairman and Heinrich Eies as secre- 

 tary. The section took up the reading of papers in Group C as follows : 

 Petrologic, Mineralogic, and Economic : 



GRAPHIC METHOD OF BEPRESENTINa THE CHEMICAL RELATIONS OF A 

 PETROaRAPHIC PROVINCE 



BY FEANK D. ADAMS 



The paper described a method by which the results of individual analyses, 

 after having been plotted in the form of curves, may be combined, so that a 

 warped surface is obtained on which are expressed the chemical relationships 

 of the rocks of an entire petrographic province. 



Eiead in full from manuscript. 



Discussion 



Prof. James F. Kemp: The curves of the oxides are fairly uniform in the 

 case of alumina and the alkalies. They showed the chief ups and downs in 

 the cases of magnesia and lime. The question was raised if the speaker had 

 drawn any conclusions from the regular or irregular distribution of the 

 components. 



Further remarks were made by the author. 



EFFUSIVE AND INTRUSIVE IN THE QUANTITATIVE CLASSIFICATION 

 BY ALFRED C. LANE 



(Abstract) 



Ludwig has made experiments to show that at high pressures (6,000 to 

 3,000 atm.) Al and Bi become bivalent instead of trivalent. If this be true 

 for Fe, then : 



2 Fe-.0 — + H — O— ^Z^ Fe^ — Og — +H 

 Intrusive Effusive 



a reaction confirmed by the fact that the average analysis of gabbro (Daly) 

 contains more ferrous iron than the average basalt, and by the fact that the 

 ferrous or hydroxyl-containing components of gabbro appear as brotocrystals 

 in basalt. 



According to Rule (7) for calculating norm, every molecule of ferric iron 

 means three of Fe which might otherwise be combined with SioOz. Thus if 

 the norm contains free silica, three molecules of free silica might be combined 

 as femic, or 9 per cent SiOz, for each 8 per cent FejOg transferred from Q to 

 FEM. Thus identically the same chemical magma may as an effusive be 



