374 C. Able — Atmospheric Radiation of 



This atmospheric radiation, moreover, continues day and night 

 and is much more effective in direct cooling than the solar 

 radiation is in direct warming. Since the loss by radiation may 

 according to Prof. Hutchins, be far greater even than this and 

 since Maurer's figures represent only an average for all kinds 

 of weather we are fully entitled to at least the general statement 

 that the cooling by radiation is to only a very slight extent off- 

 set by the direct absorption of solar heat and that its coefficient 

 may vary from the minimum value of 01° C. per hour, as pre- 

 viously computed, up to an unknown and much higher limit. 



The actual rate of cooling varies approximately as the dif- 

 ference of temperature of the radiating mass and its enclosure 

 and this is probably least in the mid-atmosphere as before 

 stated and must increase as the mass sinks to the region where 

 the colder terrestrial surface becomes an integral part of its 

 enclosure and especially when the effect of conduction to that 

 surface is superadded. 



(12.) The thermodynamic warming by compression takes 

 place at the rate of about 1° C. for each 100 meters of descent. 

 As the coefficients of absorption and radiation are uniform for 

 equal masses or for equal changes in barometric pressure as we 

 descend in the atmosphere, the thermal effects therefore vary 

 more rapidly for a given change of altitude at low levels than 

 at high levels ; therefore in the early stages of any descending 

 motion the downward movement may be accelerated but there 

 will be a tendency towards a steady rate of descent such that 

 the loss of temperature by radiation exactly counterbalances 

 the gain by compression. If we accept Maurer's coefficient 

 and diminish this by a unit in the seventh decimal place 

 in order to allow for the absorption of solar heat, as just cal- 

 culated above, we have a resultant 000,0006 gram-calories 

 as the loss of heat on the average of twenty-four hours ; this 

 corresponds to a diminution of temperature of 2*88° G. per 

 day and if this is to be compensated by compression it will 

 require a descent at the rate of 288 meters per day ; a more 

 rapid cooling by radiation, such as is required by Hutchins' 

 coefficient, would require a proportionately rapid rate of 

 descent. Such a thermodynamic compensation would bring 



binations are possible then these take place and generally with an evolution of 

 heat (the latent heat of combination). The continued evolution of this heat com- 

 pensates for further cooling by .expansion just as the latent heat of vapor operates 

 in Espy's theory of storms; when however the combined gases have further 

 cooled by expansion and radiation as they ascend until the molecules of the new 

 complex gases can form clouds of vapor there forms an outer layer of radiating 

 cloud matter such as we call the surface of the sun If the colder vapors, at 

 this surface, are by any process drawn down or if by condensation they sink at a 

 steady rate, they are again warmed up by compression, the descending gas be- 

 comes clear and may pass through the dissociation stages by absorbing a new 

 quantity of heat radiated from the solar nucleus which heat is in turn to be lost 

 by radiation in the subsequent ascension. 



