288 I >r. < 1. .F.'lmston.' Stmicy. 



Init also all the other ait rat-tin-; molecules which provide the fieM of 

 force. 



[So again with reference to the never-ceasing turmoil which goes on 

 in the atmosphere, which near the surface of the earth exhibits itself 

 in tempests, thunderstorms, and other phases of weather, and which 

 in the tipper regions includes phenomena still more extensive and 

 swift. It is manifest that these events increase the opportunities 

 which gaseous molecules have of escaping from the earth, and that 

 accordingly flm/ //m.<// tl:> H into '"/ ll int( 1 either explicitly or implicitly, 

 in every valid inquiry as to the rate of escape. 



To take them into account in an investigation based on the partition 

 of energy, we have to extend that partition to whatever agency pro- 

 duces the turmoil. Now the activity within the atmosphere (and in 

 fact almost every molar activity upon the earth other than the little 

 which is attributable to tidal action or to such minor agencies as earth- 

 quakes and volcanoes) is caused by the shiftings about of energy 

 which come in between the continuous advent of energy by radiation 

 from the sun, and its continuous escape from the earth by radiation 

 into space. Hence to render an investigation by the Boltzmann- 

 Maxwell law valid it is necessary to extend the partition of energy 

 beyond the atmosphere first to the solid earth, so as thereby to take 

 account of the anisotropic character of some of the atmospheric strata 

 (which facilitates the escape of gas) ; and secondly to embrace at least 

 the sun and the aether between the earth and sun, so as thereby to 

 take into account the turmoil in the upper regions of the atmosphere 

 (which further increases the rate of escape). It seems to be only when 

 these extensions shall have been effected that a generalised law such 

 as the Boltzmann-Maxwell law for the partition of energy between the 

 various degrees of freedom can become competent to furnish any 

 information with reference to the rate at which gaseous molecules 

 actually do escape from the earth. July 17, 1900.] 



Then as regards temperature. The temperature of a solid is in 

 reality twofold ; it is either its radiation temperature or its conduction 

 temperature. These are physically distinct, although in all but some 

 exceptional cases they are so nearly proportional to one another that 

 they may be given the same mathematical expression. So, again, when 

 dealing with gases we do well to keep in mind the essential distinction 

 between radiation temperature and what may be called convection 

 temperature. The temperature of an isolated gaseous molecule moving 

 by itself through space is of the first land only, and depends exclu- 

 sively on the energy of the internal motions those motions within 

 the molecule which enable it to absorb or emit radiant heat and it is 

 in no degree affected by the kinetic energy of the translational motion of 

 the molecule ; whereas if the same molecule form part of a gas, it meets 

 with encounters with other molecules or with the walls of a containing 





