298 Intelligence and Miscellaneous Articles. 



mena of rarefied gases, the electricity is conducted to the gas en- 

 closed in a glass tube through metal wires fused into the tube. 

 Since the metals are very likely to exert an influence upon the 

 phenomena, I have tried the insertion of a liquid between the 

 metal and the gas, in order, to some extent, to form liquid electrodes. 



A glass tube twice bent at right angles contained in its wider 

 parts fused-in platinum wires and concentrated sulphuric acid, the 

 latter rising one centimetre above the wires. The tube was joined 

 by fusion to a mercury air-pump, the drying-vessel of which was 

 filled with solid phosphoric acid. 



The gases contained in the tube and the pump having been so 

 far rarefied that an induction- current could pass through, the 

 platinum wires were connected with the poles of a Euhmkorff in- 

 ductorium, which, excited by four Bunsens, gave a striking-distance 

 of 71 millims. and a deflection of 50 scale-divisions on a mirror- 

 compass. (A constant current of 0*00035 Siemens-Daniell unit 

 gave, on the same compass, with the same spirals, a deflection of 

 100 scale-divisions. The value of the 50 scale-divisions of the 

 momentary current, calculated from the duration of a vibration of 

 the damped magnet and from its logarithmic decrement, amounted 

 to 0-000013 S.-D. unit.) 



The luminous phenomena observed in the tube under these cir- 

 cumstances are in general similar to those seen in tubes the wires 

 of which are provided with metal disks. 



The positive light starts from the bounding line of the surface 

 of the liquid and the glass wall, and spreads, in narrower or wider 

 strata (according to the strength of the pressure of the gas), to the 

 vicinity of the uegative liquid. 



From the surface of the negative liquid itself there rises, at some 

 distance from it, a slightly conic ring of light, similarly to the flame 

 of a ring-shaped burner. The intensity of this ring diminishes 

 from below upwards. The more the rarefaction increases, the more 

 does this negative luminous cylinder lengthen, and the greater 

 becomes its distance from the surface of the liquid. With the 

 strongest rarefaction the luminous phenomena are almost the same 

 at both poles. The negative light makes its appearance also in the 

 narrow parts of the tube *. "When the entire tube is inclined so 

 that the liquid surfaces are bounded by ellipses, the positive light 

 emanates from the highest part of the boundary, the negative is 

 most intense at the lowest point, but the entire ring of light remains 

 parallel to the sides of the tube. 



The magnetic deflection of the positive and the negative light is 

 the same as that in the before-mentioned tubes with metal disks. 



The whole tube is besides filled with diffused glittering light, 

 which when nitrogen is present is greenish (according to Morren 

 proceeding from the formation or decomposition of the compound 

 JN"0 3 + 2S0 3 ); without nitrogen it is bluish, and then perhaps 

 arises from the vapour of sulphuric acid. This light can be insu- 

 lated ; and then it gives a continuous spectrum. 



The entire luminous process is accompanied by decomposition of 

 * Goldstein, Berl. Monatsber. May 1876, p. 279. 



