GEOPHYSICAL-CHEMICAL PROBLEMS — SOSMAN. 231 



The atmosphere. — The physics and chemistry of the atmosphere 

 considered as a chemical unit or aggregate, while logically a part of 

 geophysics and geochemistry, are usually considered to be part of 

 the province of meteorology ; and in fact most of the investigations 

 in this field are being made by meteorologists or physicists em- 

 ployed in meteorological organizations. These questions will there- 

 fore not be further considered here. Data bearing on the origin of 

 the earth's atmosphere and its possible changes of composition in the 

 past — for example, the composition of the gases found in rocks and 

 the gases dissolved by the waters of the oceans — are, however, of di- 

 rect interest to the present Section. 



LARGER UNITS. 



The larger units of matter at the earth's surface are for the most 

 part covered by other Sections of the American Geophysical Union. 

 The atmosphere as a unit is treated by the Section of Meteorology and 

 the atmospheric-electric branch of the Section of Terrestrial Mag- 

 netism and Electricity ; the oceans by the Section of Physical Ocean- 

 ography ; the large land masses by the Section of Geodesy ; volcanoes 

 as units by the Section of Volcanology. 



The larger geologic units (for example, petrographic provinces) 

 and the rocks, considered as geologic units, might be considered to 

 fall within the province of geology rather than geophysics, and the 

 same may be said of the earth's glaciers and ice sheets. 



There are certain problems connected with these larger units, 

 however, that may be neglected by the Sections mentioned, not from 

 any lack of appreciation of the importance of the problems, but 

 solely by reason of lack of training and lack of acquaintance on the 

 part of their personnel with the technique involved; just as some 

 of the geophysical-chemical problems mentioned above may be, rela- 

 tively, neglected by reason of the geophysical chemist's lack of train- 

 ing in other branches. For example, the physics of the flow of a 

 glacier, considered as a unit, is not likely to be adequately handled 

 by those trained only in the methods of glacial field geology, and 

 it very properly becomes a subject for research under the present 

 Section. The question of the chemical composition of a particular 

 stratum of the atmosphere and the chemical equilibrium obtaining 

 therein, while of great importance to the meteorologist, might fail 

 of adequate treatment by an organization numbering no chemist 

 on its staff. The distribution of certain rock-forming oxides ac- 

 cording to "petrographic provinces" may be of primary interest to 

 the geologist, yet the physico-chemical basis for that distribution — 

 the question whether it represents an "original heterogeneity" or 

 result of differentiation — is a problem for this Section. The flow 

 of rock aggregates of varying composition, again a matter of 



