Discontinuity in the Phenomena of Radiation 79 



to another in these small scale phenomena. Besides, as I indi- 

 cated at the beginning of this paper, it is not in the magnitude of 

 the phenomena nor in its extreme brevity that the discontinuity 

 arises. In order to obtain by logical reasoning Planck's partition 

 of the energy, which is undoubtedly extremely near to the truth, 

 and avoid equipartition, which is certainly far from it, we are 

 bound to assume some hypothesis concerning the radiation of 

 energy for which we have no basis in our fundamental principles. 

 It seems necessary to postulate a picture of the atom structure 

 such as the following. Around the positively charged nucleus 

 of the atom we have negative electrons rotating in orbits. On 

 the older views the positions of these orbits could change con- 

 tinuously as the electrons gained or lost energy in a continuous 

 manner. On the new idea, we must consider the possible orbits 

 as discrete and well separated from one another. While an 

 electron moves in one of these stable paths, its motion can be 

 calculated by the orthodox dynamical rules ; thus for a single 

 electron whirling round a single nucleus (the usual view of the 

 hydrogen atom), any of these paths would be the usual planetary 

 ellipse. While in this path the energy of the electron remains 

 constant ; there is no radiation of energy and no absorption. 

 Some critical condition arises due to external influences 

 and the electron leaps suddenly from one orbit to another. As 

 the energies of the electron in two orbits are different, the 

 electron must part with or absorb some energy in the transit, the 

 amount being quite definite and determined by the particular two 

 stable orbits considered. This amount is emitted or absorbed as 

 vibrational energy of a definite frequency, and here the significance 

 of Planck's constant comes in, for the frequency of the radiation 

 emitted or absorbed must be such that when multiplied by this 

 constant the resvdt is the amount of energy in question. This is 

 a view of atom-structure which is receiving considerable attention 

 of late. You will see that it postulates both discontinuous 

 absorption and emission. Planck, himself, being reluctant 

 to abandon any more than was necessary of the older theory 



