September 21, 1917] 



SCIENCE 



275 



these numerous investigations are the dis- 

 coveries that negative electricity occurs in 

 multiples of a perfectly definite and accu- 

 rately measurable unit; that this unit, the 

 negative electron, perhaps in large num- 

 bers, is at least an integral part of all 

 atoms; that electrons often are ejected 

 from an atom ; that when ejected they leave 

 with enormous velocities ; that when in mo- 

 tion they possess inertia; and that this in- 

 ertia increases with the velocity. 



Naturally such discoveries suggested the 

 Saturnian and other similar atomic mod- 

 els, several of which have been elaborately 

 discussed. 



6. In 1906 the author^ computed the pos- 

 sible magnetic field of a Saturnian atom 

 and found in this field a vera causa, per- 

 haps an adequate cause, of the hitherto un- 

 explained pressure shift of spectral lines. 

 A simple presentation of the argument is 

 as follows : 



Assuming Thomson's Saturnian atom of 

 revolving rings of electrons, it seems prob- 

 able that the wave frequency of the radia- 

 tion emitted by any one of the rings of a 

 given atom may be a simple multiple of its 

 orbital frequency. Any bunching, for in- 

 stance, of the electrons, however tempo- 

 rary, would produce radiation whose fre- 

 quency was the same as that of the com- 

 plete orbital revolutions. But this revolu- 

 tion of rings of electrons, presumably 

 around a common axis, constitutes so many 

 circular electric currents which obviously 

 produce solenoidal magnetic fields, and 

 themselves are subject to inductive effects. 



Now it has been shown by Langevin*' that 

 in the case of a ring of electrons any forced 

 change in the magnetic flux merely alters 

 the orbital speed without changing the 

 radius. Hence the self induction remains 

 constant and if E be the induced electro- 

 motive force, then 



Astrophys. Jr., 23, 233, 1906. 



8 Journal de Physique, 4, 678, 1905. 



E^Lj^ + m, 



in which L is the self-induction, R the 

 ohmie resistance and i the strength of the 

 current. But in the case of an atomic ring 

 of electrons E = dN/dt = Ta.te of change 

 of magnetic flux through the ring, and 

 R = 0, presumably. 

 Hence 



and 



That is, the induced current in the ring is 

 directly proportional to the change in the 

 magnetic flux through it. Furthermore, 

 the induced current is permanent instead 

 of momentary as in ordinary circuits, so 

 long as the change in N is permanent. 



In this connection it is interesting to note 

 that Kamerlingh Onnes' has recently shown 

 by a series of brilliant experiments that an 

 induced current may last for hours with 

 but little reduction (less than 1 per cent, 

 per hour) in a lead wire solenoid at very 

 low temperatures. 



Now, from the Zeeman effect it is obvious 

 that radiating atoms are acted upon by an 

 external magnetic field, and, therefore the 

 inference is immediate that these atoms 

 themselves possess magnetic fields of their 

 own — they could not othenvise be acted 

 upon by a magnetic force. Also, since the 

 the kind and magnitude of the Zeeman 

 effect is independent of temperature, as 

 shown by both radiation and absorption, it 

 follows that the atomic field must also be 

 independent of temperature. 



Further, as magnetic fields are known 

 always to exist in connection with electric 

 currents, and not certainly known ever to 

 be due to any other cause, and as moving 

 electrons constitute the only kno\^Ti electric 



7 Nature, 93, 481, 1914. 



