310 Prof. L. T. More and Mr. E. G. Rieman on 



The direction in all cases is as if there were a virtual anode 

 at jt>, due to a piling up of positively charged ions, and a 

 positive current flowing toward each of the two ends, D and 

 C, as shown by the arrows. The discharge can also be 

 shown to be intermittent either by viewing it in a rotating 

 mirror or by the fact that when it is intense it gives out a 

 high-pitched musical note. 



Professor Pighi explains all these actions by assuming 

 the magnetic rays to be due to what he calls planetary 

 doublets (Doppelsterne) which consist each of a gas or metal 

 ion, positively charged, and an electron revolving about it in 

 an orbit. The bond of electrical attraction between them, 

 due to their distauce apart, is of such a magnitude that 

 they may be classed as intermediate between a neutral atom 

 and an atom entirely dissociated into an ion and an electron. 

 He supposes that in a Geissler tube, and especially near the 

 region of the second cathode bright space where there are 

 many positive ions and electrons moving in opposite direc- 

 tions, neutral systems of particles exist in addition to the 

 free, dissociated ions and electrons. These systems are of 

 two kinds : neutral atoms which are formed when an elec- 

 tron with the proper speed comes so close to an ion as to 

 be captured by it and held in a permanent chemical bond, 

 and doublets where the speed of an electron is such that, 

 while it is captured by the ion, they do not coalesce. The 

 result in the second case is that the electron revolves 

 about the ion as a satellite and forms an electrically neutral 

 system, which is not very stable. Ordinarily these doublets 

 are comparatively few in number and so short lived as not 

 to be detected. Such a doublet, while it persists, should act 

 like a magnetic shell, since the motion of the electron makes 

 it equivalent to a small closed electric current. 



As the presence of a magnetic field causes these doublets 

 to persist, it must be shown that the magnetic force exerts 

 a mechanical force on the system tending to increase its 

 stability. The simple case of an electron rotating about a 

 positive ion in a plane perpendicular to a uniform magnetic 

 field has been discussed by Professor Righi, and he has 

 shown that there is a resultant electromagnetic force on the 

 electron in the plane of rotation and radial : either towards 

 or away from the centre, depending on the direction of 

 rotation of the electron. Consequently, all those doublets 

 having a rotatory motion in one sense will have their 

 stability increased by a given uniform magnetic field, and 

 those whose motion is in the opposite sense will be destroyed. 

 If, however, the magnetic field be not uniform, then the 



