392 Prof. B. Wiedemann on the 



obtained with phosphorescent solid bodies, and further assume 

 that the platinum emits all its energy in rays situated in the 

 infra-red (we know that the greater portion of the radiation 

 falls there), and put E = 2*2 x 10*, 6 = 10 3 , a = 2:— 



a K =:3-5xl0- 10 millim. 



a A =2*l „ 



If here also we put 6 = 10 8 , we should have 

 a K =l*l x 10~ 12 millim., 

 a A = 6'6 xlO" 3 „ 



If now we compare the values obtained for the amplitudes 

 a K and a A with the diameter of the molecules, for which the 

 data of the kinetic theory of gases gives numbers of the 

 order 10 -7 millim., we obtain the following results. 



If in the platinum the store of luminous energy results from 

 vibrations of the luminiferous gether, the amplitude of the 

 sether must amount to ^ Q millim. or more, which cannot be 

 imagined ; consequently the store of luminous energy must 

 reside in the vibrations of the material molecules themselves. 



The same holds also for sodium, for here also the amplitudes 

 of vibration of the sether-particles reach magnitudes a thousand 

 times greater than the dimensions of the molecules. 



If we assume, on the other hand, that the vibrations of the 

 material molecules are the cause of the store of luminous 

 energy, then the errors in both cases are only small fractions 

 of the diameter of a molecule, which is immeasurably more 

 probable. 



For the sake of control let us ask what value b must have 

 so that, in the vibrations of the aether- atmosphere in glowing 

 platinum, the amplitude may be equal to the diameter of the 

 molecule 10 -10 metre, or 10 -7 millimetre. 



We obtain from the above equation for # A 2 , if we put 

 « A =10~ 10 , for platinum, 



1 _ (10-") 2 xl-3xl0 6 x2 2 _ 



b" 2-2 xlO 4 " MX1U ' 



If, again, at the time t — Q the intensity is i 0) then 

 If 



it=he~ bt , \og % 4 = -bt. 



l t — Jq*oj then bt=l, 



t = I = 2-4 x 10- 18 seconds ; 

 b 



