F. W. Very — Transmission of Terrestrial Radiation. 517 



this constitutes a final disposal of the heat. The thermal 

 energy is still imprisoned. Its only way of escape is through 

 the gradual processes of internal radiation which are found to 

 be most fundamental and at the bottom of all of those physical 

 properties which we call "atmospheric."* 



If any layer of the atmosphere deserves to be called " the 

 effective radiating layer," it is the isothermal layer, where con- 

 vection being no longer potent, the heat obtained by absorp- 

 tion of the incoming solar rays must be radiated back to space, 

 since it can not accumulate indefinitely. There is no evidence 

 whatever of Angstrom's effective radiant layer of the atmos- 

 phere at 3000 meters. On the other hand, the peculiarly 

 potent radiation-function of the isothermal layer of the atmos- 

 phere has been repeatedly pointed out by me.f 



Here is the source of the fallacy : The 0*15 — -. — '—. — of ob- 



cm min. 



served terrestrial radiation goes out scot free, and the trans- 

 mission of terrestrial radiation is truly 30 per cent in the given 

 case. Most of the remaining 70 per cent is not directly trans- 

 mitted to the " colder layers " at 3000 m , there to be absorbed ; 

 and still less does any portion of the 30 per cent linger there, 

 as Angstrom supposes ; but the 70 per cent is mainly absorbed 

 within a few hundred meters of the surface, at most, and is 

 thereafter indirectly transmitted to space through the step-by- 

 step process of alternating gaseous absorption and reradiation 

 which is described in my treatise on " Atmospheric Radiation," 

 published in 1900. Included in the 70 per cent, there may be 

 an absorption of 2 or 3 per cent which is special to ozone in 

 elevated regions of the air.:}; Unless the 70 per cent absorbed 

 by the air were also " transmitted " in the end, though in its 

 own slow way and through a complex of radiation, convection, 

 penetration, aqueous condensation and evaporation, etc., which 

 can scarcely be attacked in any other way than by the methods 

 of thermodynamics, the earth's surface would all the time be 

 getting hotter, since it receives fresh accessions of heat from 

 the sun's rays every day. Some portions of this atmospheric 

 thermal energy are radiated directly to space by cloud sur- 



* In confirmation of this assertion, I will merely note that the first differ- 

 ences of the radiant potential of the air in a vertical section through the 

 atmosphere form a curve which agrees precisely with the curve of the verti- 

 cal distribution of density, proving that it is the radiation between the air 

 molecules which governs the kinetic mechanism of the gaseous mass. 



f Compare " Atmospheric Radiation," Bulletin G, TJ. S. Weather Bureau, 

 1900, p. 123; " The Solar Constant," Weather Bureau Pub. No. 254, 1901, 

 p. 25 ; Astrophysical Journal, vol. xxxiv, p. 386, December, 1911 ; and 

 especially the paper: " Sky Radiation and the Isothermal Layer," this 

 Journal, vol. xxxv, pp. 369-388, April, 1913. 



% See my quantitative measurements of this absorption, Science, N. S., 

 vol. xl, p. 421, September 18, 1914. 



