[eve] the constitution of the ATOM 11 



placed end to end, a number of small magnets with an electron con- 

 strained to move in a circular path around the line of magnets. With 

 this hypothesis he was able to account correctly for the above law 

 for series of lines in the spectrum. 



We may appreciate Poincaré's criticism — "On a quelque peine à 

 accepter cette conception, qui a je ne sais quoi d'artificiel." 



Inasmuch as physicists endeavour to explain magnetism in terms 

 of revolving electrons, there is a lack of simplicity, and there is an 

 inconsistency, in introducing elemental magnets inside the atom. 

 Nevertheless, it must be admitted that Weiss has found remarkable 

 evidence for the conception of magnetons, or elemental unit magnets, 

 producing intra-molecular fields reaching to millions of Gauss units, 

 far transcending any produced by our most powerful electro-magnets, 

 and difficult to explain by revolving electrons. 



Again to quote Poincaré — 



"Qu'est-ce maintenant qu'un magneton Est-ce quelque 



chose de simple? Non, si l'on ne veut pas renoncer à l'hypothèse 



des courants particulaires d'Ampère; un magneton est alors un 



tourbillon d'électrons, et voila notre atome qui complique de 



plus en plus." 



Perhaps the hypothesis of Bohr, explained later, may overcome 

 the difficulty, but for some time to come, the more prudent will sus- 

 pend judgment on the magneton. 



Recently there has been nothing short of a revolution in Physics. 

 In certain domains, the leading workers and thinkers have deliberately 

 abandoned the classical dynamics and electro-dynamics, and made 

 suppositions which are in direct opposition to these. This startling 

 change may perhaps be justified by the fact that the famous laws 

 and equations were based on large scale experiments, so that they do 

 not necessarily apply to conditions within the atom. Those who put 

 forward and make use of the new hypotheses, men like Planck and 

 Lorentz, Poincaré and Jeans and others appear to do so with reluc- 

 tance, like a retiring army forced from one position to another. Others 

 like Rayleigh and Larmor appear to regard the whole movement with 

 misgivings, and some endeavour like Walker and Callendar to find a 

 way out. There is a young school who go joyfully forward, selecting 

 and suggesting somewhat wild hypotheses, and yet attaining an 

 unexpected measure of success by their apparently reckless methods. 



The main phenomena to which the new mechanics have been 

 applied are the radiation within an enclosure, and the distribution 

 of energy therein; the high speed of electrons ejected from matter 

 by ultraviolet light, or by Rôntgen rays, or by the gamma or pene- 



