OKIGIN OF ATMOSPHERE AND OCEAN 247 



consisted of the gases of lower molecular velocities. The carbon dioxide 

 seems to have been the first of the atmospheric constituents to be re- 

 tained on the surface of the growing globe. The enlargement of the earth 

 and of its attractive power added the lighter gases to its envelope, and 

 the carbon dioxide has been relegated to a minor place in volume. The 

 active consumption of the gas in carbonation of the crystalline rocks has 

 been a positive reduction of vast amount. The nitrogen has suffered 

 little loss, on account of its inertness, and has become the preponderat- 

 ing element. The amount of water exhaled by the earth has been im- 

 mense, but it has been mostly condensed to liquid, and has always been 

 a small constituent of the atmosphere and locally variable, depending 

 on temperature. It could not freely escape beyond the earth's control, 

 because of its easy condensation to a liquid. The quantity of water 

 seems to vary proportionally with the carbon dioxide, as the latter is an 

 independent controlling factor of the atmospheric temperature. This 

 matter will be discussed later under climate. Hydrogen and helium 

 have never been important constituents of the atmosphere because their 

 high molecular velocities have probably carried them beyond the earth's 

 control, although it may be possible that free hydrogen in the air unites 

 with oxygen or other elements. 



Under the new hypothesis the atmosphere becomes a subject of geology. 

 Its origin and its history, as well as its present constitution, are subjects 

 not merely of speculation, but of geologic investigation, and the branch 

 of geology called " atmospheric" will have a much broader field than 

 merely rock-weathering and wind deposits. 



Origin of the Ocean 



Like the atmosphere, the hydrosphere is volatile matter pressed out 

 from the lithosphere, and the ocean-making process is still active. In 

 volcanism we see today one conspicuous method by which water is trans- 

 ferred from the interior to the surface of the globe. The existence of 

 water in the earth's interior, even in the quartz of the crystalline rocks, 

 has not been sufficiently emphasized. It is not necessary to assume that 

 all the contained water exists as such in the deeps of the earth, as it may 

 be produced in part in the superficial zone by union of the elements or 

 by chemical reaction. Perhaps Siemens was right in his conclusion that 

 large quantities of free hydrogen, or hydrogen compounds, from the 

 earth's magma are explosively oxidized in the volcanic chimneys. 



The seas could not form until the atmosphere had accumulated suf- 

 ficiently to hold sun heat that would give the earth a surface temperature 

 above the freezing point. Below this temperature the water which was 

 forced from the earth's interior must have frozen in or on the cold sur- 



