76 



SCIENCE 



[N. S. Vol. XLI. No. 1046 



the atom seems to reside in the nucleus. 

 For if the size is extremely small its elec- 

 tromagnetic mass would — from the formula 



2/3 ^be relatively large. So its mass 



might be 1,800 times that of the electron 

 (and J. J. Thomson's experiments suggest 

 that no positive carrier has a mass smaller 

 than that amount) provided its diameter 

 were only 1/1,800 that of the electron. 

 From such consideration Rutherford^* 

 thinks it probable that the nucleus of the 

 H atom is, in fact, the long-sought positive 

 electron. 



Attention has been forcibly drawn to 

 the nucleus type of atom within the past 

 year and a half by the extraordinary suc- 

 cess it has had as interpreted by Bohr, 

 Darwin and Moseley, in accounting for 

 the exact position of lines in the spectra of 

 gases. Their work has also served to bring 

 into the limelight the earlier and perhaps 

 equally striking work of J. W. Nicholson. 

 In November, 1911, he published a paper^^ 

 in which he assumed the existence of sev- 

 eral elements with atoms of very simple 

 and definite structure. One of these he 

 called nebulium. In the neutral condition 

 it was supposed to have a positive nucleus 

 with charge 4 e, and around it at equal 

 distances apart in a circular path, rotated 

 four electrons each with unit charge e. 

 It might, however, lose one electron, when 

 it would become positively charged, its 

 three electrons now taking up new positions 

 a third of a circumference apart. Simi- 

 larly he supposed that the atom might take 

 up more electrons, and have a negative 

 charge. 



He discussed mathematically the vibra- 

 tory motions of such an atom and showed 

 what kind of a spectrum the radiation 

 would furnish. The theoretical analysis of 

 the spectrum of his imaginary element 

 nebulium showed that all the characteristic 



nebula lines of the Great Nebula in Orion, 

 leaving out those due to hydrogen and 

 helium, could be attributed to the vibrations 

 of the nebulium atom, except two lines. On 

 the very day he read this paper in England 

 a German astronomer, M. "Wolf ,^* presented 

 a paper in Heidelberg which described the 

 discovery that different lines of this nebula 

 were due to radiation from different parts 

 of the nebula, and that these two lines 

 which Nicholson had found exceptional 

 were due to a radiating source different 

 from that of the other lines. Whereas al- 

 most all the lines were due to radiation 

 from the bright ring of the nebula, these 

 two lines were caused by radiation from 

 different parts of the nebula, that for one 

 of them coming from the dark central 

 space and for the other chiefly from the 

 outer edge of the ring. All other lines had 

 their maximum brightness in the bright 

 ring itself. 



Another imaginary substance which 

 Nicholson named protofluorine, he suc- 

 ceeded in connecting in a similar way with 

 the spectrum of the sun's corona.^' This 

 atom he supposes to have — when neutral — 

 a nucleus 5 e with 5 electrons in a circular 

 orbit about it. He analyzes its radiation on 

 the assumption that it gives forth radia- 

 tion energy in quanta, as Planck has sup- 

 posed. He anticipates Bohr in the empha- 

 sis he gives to the idea of constancy of 

 angular momentum in the rotating elec- 

 trons. His calculations on this protoflu- 

 orine atom account satisfactorily for the 

 existence of fourteen out of the twenty-two 

 lines of the corona spectrum, with an aver- 

 age difference of less than one part in a 

 thousand between observed and calculated 

 values. His calculations also show the 

 magnitude of the positive or negative 

 charge of the atoms originating the vari- 

 ous lines. He concludes that in these 

 primitive forms of matter — nebulte and 



