SOME CONTEMPORARY ADVANCES IN PHYSICS— X 127 



It may be recalled from the First Part of this article that the different 

 Stationary States of a group, sharing a common value of n and a com- 

 mon value of k, are distinguished from one another by having different 

 values of a numeral which was designated by j and called the Inner 

 Quantum-number. It was so chosen that the only transitions which 

 occur are those in which j change by one unit, or not at all; while 

 transitions between two states, in each of which j = 0, are likewise 

 missing. This numeral is correlated with the angular momentum Pa 

 of the entire atom, in the theory here outlined. For systems of even 

 multiplicity. Pa is equal to jh/2ir\ for systems of odd multiplicity, 

 Pa is equal to (7+^) h/2Tr. 



The various Stationary States of a group differ slightly in energy — 

 otherwise, of course, they would never have been discerned. The 

 energy-value of an atom must be conceived therefore as depending 

 not merely upon 71 and k, not merely on the rates at which the two 

 whirling parts are separately spinning, but likewise upon their mutual 

 orientation and hence upon 7. In this theory, the dependence of energy 

 upon orientation must be postulated outright. We shall presently 

 meet with a case in which the dependence of energy upon orientation 

 can be foreseen, even in detail. 



It appears from all these speculations, that a transition between 

 two Stationary States is no longer to be conceived merely as a simple 

 leap of an electron from one geometrically-definite orbit into another. 

 A leap is indeed supposed to occur, but it is accompanied by a turning- 

 inward or a turning-outward of the axes of rotation of the two spinning 

 parts of the atom. The radiation which comes forth is a joint product 

 of these two processes, in which however no features of either separ- 

 ately appear; only the net change in the energy of the atom, the 

 algebraic sum of the energy-changes due to each process separately, 

 is radiated as a single fused unit. Nature does not make the separ- 

 ation which our imaginations make. 



T. Magnetic Properties of Atoms 



Having used an orientation-theory to interpret the complexity of 

 the Stationary States, we will now consider an orientation-theory 

 developed to account for the effect of a magnetic field upon the Station- 

 ary States. There, it was supposed that the various States belonging 

 to a single group are distinguished by various orientations of two 

 spinning portions of an atom, relatively to one another. Here, it will 

 be supposed that the various States which replace each individual 

 State, when a magnetic field acts upon the atom, are distinguished 



