133 Prof, Plucker on the Action of the Magnet 



a luminous magnetic surface as the geometrical locus of the mag' 

 netic cunws passing through the separate points of the platinum 

 wire. 

 Bonn, December 27, 1857. 



Addition to the above. By M. Plucker. 



39. Ill accordance with the ph?enomena described in the 

 latter part of the preceding paper, we may say that electric 

 light under the circumstances in point is magnetic^. Inasmuch 

 as such light, which proceeds from one point of the negative elec- 

 trode in all directions, is drawn together by the magnet to a 

 luminous magnetic curve passing through the same point, the 

 original rays behave as iron-filings would do if we imagine them 

 infinitely fine, perfectly flexible, and attached to the point of the 

 electrode in opposition to the force of gravitation. This magnetic 

 behaviour is entirely distinct from the effect of the magnet upon 

 the luminous magnetic currents. The pliajnomenon in question 

 reappears in precisely the same manner, as I have already proved, 

 after inversion of the magnetic poles, whence we may conclude 

 it to be altogether independent of the direction of the discharge 

 of the electric current. 



40. This last hypothesis was most distinctly supported by the 

 following experiment : — A tube was taken which, as before, had 

 a bulb fused on to one end. The negative platinum electrode 

 was introduced into the bulb, so as to form one of its diameters 

 perpendicular to the axis of the tube. Tiie two ends of this elec- 

 trode, which was thus fused into the glass in two places, were 

 connected together outside the bulb. The bulb was placed upon 

 the approximated armatures in sueli a manner that the tube was 

 in a vertical, and the horizontal electrode in an equatorial posi- 

 tion. On discharging, as before, Ituhmkorfi''s aj)paratus through 

 the tube, light emanated from every point of the electrode 

 through the bulb, and this light collected to a curved surface, 

 which, forming a bridge from one polar surface to the other, 

 consisted of the illuminated magnetic curves passing through 

 the separate points of the electrode. This surface remained per- 

 fectly firm and immoveable when the bulb with the tube was 

 turned to any extent around the platinum wire, which formed a 

 horizontal diameter of the bulb. It also remained unaltered even 

 when tlie tube (and therewith the path of electrical discharge) 

 was turned obliquely to the horizon, vertically or horizontally, 

 and in the latter position the tube might reach above the one or 

 other armature, away from the place of maximum magnetic 

 action, without altering this surface. 



* These phfenomena appear most beautifully in the wide cylindrical 

 tubes lately made by M. Geissler. 



i 



