Vol.. 6, 1920 
GEOPHYSICS: R. B. SOSMAN 
597 
solution and redeposition, as well as the forces exerted in their recrystal- 
lization, are of particular interest. The structures resulting from move- 
ment in silicate rocks under differential pressure are in. need of quantita- 
tive study. Transfers of mechanical energy and its conversion into heat 
are also involved. Consolidation and recrystallization as a direct result 
of uniform pressure are likewise to be considered. 
Mention should be made in this connection of the physics and chemistry 
involved in faulting as well as in jointing and minor movements of the 
solid rocks. These phenomena have often been treated under the prin- 
ciples of elastic theory as applied to homogeneous bodies, yet there can 
be no question that the elastic properties and conditions of rupture of ag- 
gregates must differ in many essential particulars from those of homo- 
geneous bodies. Here is a considerable field for experimentation. 
Bodies of Water and the ''Chemical Sediments'". — The chemistry of the 
deposition of salts from sea- water has already been made the subject of 
special research, and van't Hoff's results in this field are already familiar. 
The deposition of calcium carbonate awaits a similar thorough study. 
Allied questions are the formation of dolomite, the deposition of various 
salts from inclosed bodies of water, the deposition of phosphate rocks, 
the precipitation of colloidal suspensions of clay and other substances, 
and the origin of the great deposits of sedimentary iron ore. 
Problems of fresh-water bodies and streams include the chemistry of 
bog iron ores, and the amounts of insoluble and colloidal solids and of 
soluble salts carried by streams. Problems relating to underground 
waters may also be included here, such as: the dissolving and recrystal- 
lizing activity of underground waters; connate waters and their possible 
chemical changes; movements of underground waters and their relation 
to the alteration and concentration of gas and oil; principles of hydraulics 
governing the flow of wells and springs; and the characters which will 
serve to differentiate between vadose and juvenile waters. 
The Atmosphere, — The physics and chemistry of the atmosphere con- 
sidered as a chemical unit or aggregate, while logically a part of geo- 
physics 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 employed in meteorological 
organizations. These questions will therefore not be further considered 
here. Data bearing on the origin of the earth's atmosphere and its possi- 
ble 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 direct 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. The atmosphere as a unit is treated by the 
