262 SCIENTIFIC NOTES AND NEWS 



Geological Society, which are devoted rather to the reading and dis- 

 cussion of stated papers on geological subjects; and to include in the 

 discussion problems and hypotheses which were still in an unfinished 

 or only partly developed state. 



Meetings have been held regularly at the homes of members, on which 

 account the membership has had to be restricted to forty-five. The 

 following brief list gives some of the subjects selected for discussion, 

 and will serve not only to show the kind of problems considered but also 

 to indicate the direction of petrologic thought and research in recent 

 years : 



Eutectics, in the laboratory, in the field, and in their relation to rock 

 classification. 



The role of mineralizers in magmas. 



Ore bodies of magmatic origin. 



Water as a primary agent in mineral and rock formation. 



The relation between igneous activity and movements of the earth's 

 crust, with especial reference to differentiation, the cause of "petro- 

 graphic provinces," and the hypothesis of Atlantic and Pacific kindred. 



The textures of metamorphic rocks. 



The tools and methods of petrography. 



The weathering of rocks. 



The assimilation of rocks by magmas. 



The theory of magmatic stoping. 



The forms of silica. 



The volume change of rocks on fusion. 



The mode of escape of mineralizers from deep-seated bodies of 

 magma. 



The origin of large intrusive rock bodies. 



Isostasy in its relations to petrographic provinces. 



The description of minerals, and of sedimentary, igneous, and 

 metamorphic rocks. 



The areal distribution of igneous rocks and of their chemical constit- 

 uents. 



The minor constituents of meteorites. 



Pegmatitic rocks and minerals. 



The secondary enrichment of ores. 



Volcanic gases. 



The nature and sequence of magmatic emanations, as shown by 

 pegmatites, volcanic emanations, contact deposits, and mineral veins. 



The determination of opaque minerals. 

 , The origin of the Kiruna ores. 



The sampling and chemical analysis of rocks. 



Some of the meetings have been devoted to reviews of petrologic 

 literature, such as Barker's Natural History of Igneous Rocks and 

 Bowen's Later Stages of the Evolution of the Igneous Rocks. Short 

 reports of work in progress have also been given, and the discussion 

 of the results from the field and laboratory points of view has never 

 failed to bring out aspects of interest and thus to add to the value of 



