3 o SCIENCE PROGRESS 



table from this point of view, the hypothesis being that corre- 

 sponding members of different " periods " in the table differ 

 by the numbers of the stable groups of eight electrons con- 

 tained in their atoms. Success in explaining certain magnetic 

 properties of matter is also more or less assured from the be- 

 ginning by the nature of the hypothesis. 



However, it seems to be the view of most competent physi- 

 cists at present that in the directions other than those in 

 which success might reasonably be assumed, Parson's hypo- 

 thesis has proved somewhat disappointing and unfertile. In 

 the February number of the Proceedings of the Physical Society 

 there appears a very able resume by Dr. H. S. Allen of the 

 evidence in favour of the ring electron theory, but the discus- 

 sion following Dr. Allen's paper cannot be said to have been 

 very favourable to the hypothesis. According to Dr. Allen 

 the ring electron (with some modifications of Parson's original 

 idea) can account for the facts of diamagnetism and para- 

 magnetism ; involves no loss of energy in its rotatory motion ; 

 explains certain facts concerning asymmetry of some types of 

 radiation, the effect of magnetisation of iron on its absorption 

 coefficient of X-rays, the small amount of ionisation of gases 

 due to X-rays ; it can be adapted to the Quantum hypothesis, 

 and Bohr's theory can be restated so as to apply to it ; the 

 Zeeman effect can be brought within its compass ; and the 

 problems of chemical constitution and stereochemistry may be 

 solved by it, in particular, stationary valence electrons being 

 possible (a great desideratum). As stated above, the dis- 

 cussion by other members of the Physical Society hardly sup- 

 ported Dr. Allen in his claims. The general trend of the dis- 

 cussion may be best illustrated by a few quotations from it. 



" Judged by its power of predicting new phenomena, the 

 hypothesis of the ring electron is disappointing," and " in 

 striking contrast is the fertility of Bohr's hypothesis of the 

 atomicity of angular momentum." " The value of a model 

 such as the ring electron will be judged by the number and 

 importance of the facts that it accounts for, and by the ability 

 it shows to predict undiscovered phenomena, or to suggest new 

 lines of research. The ring electron does not appear to have 

 been especially fortunate in this latter respect ; and its claim 

 to consideration must perhaps rest mainly on arguments such 



