76 M)-. Jamc'^ Iricc on 



It appears that if n is small enough or T large enough, the value 

 of r is so small that the divisor given above is little different 

 from unity and so for high temperatures or frequencies of 

 vibration not too great the equipartition principle nearly holds ; 

 but at low temperatures or high frequencies it is utterly at 

 variance with the facts. This in itself is but one way of saying 

 that, under certain restricted conditions, Newtonian dynamics 

 is an excellent approximation to truth. 



It remains for me to give you a brief statement of the 

 manner in which Planck endeavours to justify this partitioning 

 of the energy. He does so by introducing the hypotheses of dis- 

 continuous or spasmodic radiation. Now, this hypothesis can 

 find no secure position in the general framework of electro- 

 magnetic theory as built on Maxwell's Equations. According to 

 modern views as to the structure of the atom, there is no doubt 

 that the electrons of the atom are the sources of all those high 

 frequency radiations for which the principle of equipartition 

 proves such a failure. The result of applying orthodox theory 

 to the actions between electrons and the ether is to demonstrate 

 that electrons cannot radiate energy if they are at rest or in 

 uniform motion. They must be moving with velocities variable 

 either in speed or direction, or both. Now, such variable motion 

 is an obvious feature of rotation in the quasi-planetary orbits 

 around the atomic nucleus ; it is also a feature of electron motion 

 when they are ejected from the atom by the action of ultraviolet 

 light or X-rays. At all events, according to classical theory, 

 electrons whirling in their atomic orbits should be continuously 

 radiating energy. This constitutes something of a difficulty, for 

 such continuous radiation of energy must. mean a gradual con- 

 tracting of the orbit and a gradual absorption of all the electrons 

 into the necleus with a consequent change in the properties of 

 the atom which is certainly not justified by facts. The ordinary 

 phenomena of magnetism, and the action of magnetic fields on 

 sources of monochromatic light give powerful evidence of the 

 permanent and undiminished intensity of such electronic whirls 



