254 Mr. J. J. Thomson on the 



consisting of one atom of oxygen and one of 

 hydrogen, which can be formed. 



— = the time during which an oxygen atom is free 

 P from another oxygen atom. 



Then by the same principles as in § 1 the equations are 



p + 2q + r = N. 



dm 2n _ 2r 2m 2 2m 2 p 



" 



dt — *! t{ Tj T 3 





dn m 2 r n np 

 dt -"tj t d ~ t 1 ~T 2 





dp 2q r r 2p 2 np 

 dt == ^" + ^ + ?~"tT~t 2 " 



7)l 2 p 

 "^3 



dq p 2 q 



dt ~~t 4 t% 





dr np m 2 p r r 

 dt ~"t 2 t 3 t B t 3 ' 





y. ■ (i3) 



Let us begin by finding the values of m, n, p, q, r when 

 things have attained a steady staie ; we shall first assume 

 that the molecule of water is formed by a molecule of hydrogen 

 uniting with an atom of oxygen, and that when a molecule of 

 water is decomposed it splits up into a molecule of hydrogen 

 and an atom of oxygen. These assumptions are represented 

 by making t s ' and t 3 both infinite, and when things are in 

 equilibrium the above equations become 



so that 



n 



m* "^ 



*T 



>i 



r 



np 



9 



p 2 



"t 4 J 



n 2 p 



2 T 



(14) 



^3 T 2 ^2 T 2 



Now if we suppose, as in § 3, that the number of free 

 oxygen and hydrogen atoms is very small compared with the 



