54 F. W. Very — Nebulosity around Nova Persei. 



sidered to be objections to a theory of real motion can be 

 shown to be demanded by a special form of the theory, they 

 constitute a strong argument in favor of this explanation. I 

 believe that such a modified explanation is indicated. 



The difficulties urged by Perrine in regard to the sudden 

 appearance and brightening of local spots on the outer ring, 

 and the tangential motion which prevails in many features, 

 appear to him contrary to what should be expected if the phe- 

 nomenon is due to actual motion. Evidently the only actual 

 motion considered is a radial one. These difficulties which 

 form the most serious objection to such theories of actual 

 motion as have been hitherto published, become, on the con- 

 trary, a strong argument in favor of a different theory of real 

 movement. 



(4) The theory which I would propose is that of the actual 

 movement of diamagnetic ions under the control of magneto- 

 electric impulses emanating from the star and following the 

 lines of magnetic force. We may compare such a stream of 

 moving ions to the beam of light from a parabolic mirror. The 

 rays are directed and do not at once expand to fill the entire 

 sphere. Diamagnetic ions may be expected to follow lines of 

 magnetic force to regions of least potential in the magnetic 

 equatorial plane, and with only slight expansion of the tubes 

 of force through a limited range of the magnetic sphere. 

 Hence the luminosity, as in the distinct phenomenon of a 

 comet's tail, may extend to a great distance before becoming 

 too faint for observation, although of course the light must 

 eventually fade, unless perpetually renewed. This seems to 

 answer the objection on account of the long continuance of 

 the phenomenon. 



In the next place, if the structure observed in the nebula is 

 to be compared with that of a magnetic phantom, a strong 

 tangential component must enter into lines emanating from 

 the nova after these have extended to a certain distance. The 

 magnetic phantom, whether exhibited by iron filings or by 

 dust of bismuth, extends in sweeping curves from pole to pole 

 of the magnet — the only difference being that magnetic parti- 

 cles move towards the poles, and diamagnetic away from them, 

 but that both follow the lines of force. The observed trajec- 

 tories of nebulous material around the nova are in fair, per- 

 haps I should say in nearly perfect, agreement with the 

 projection of a system of lines of magnetic force. 



If the brightening or sudden appearance of new bright spots 

 on the outer ring can also be explained on this hypothesis, I 

 think it must be admitted that the facts decidedly favor, if 

 they do not demonstrate, the proposed explanation. 



Two cases may be distinguished: (a) The light is produced 



