322 SEC. 10. ELECTRICITY. 



1377. Vacuum Tube for electric discharge. 1856. 



Teyler Foundation^ Haarlem. 



Masson in Paris used a Torricellian vacuum sealed by the lamp, in his 

 extensive researches on the electric spectrum. Some time afterward, Dr. 

 Geissler, in Amsterdam, made this Torricellian vacuum at the instigation of 

 Prof. Van der Willigen, now director of the Teyler Museum, whose property 

 it is at present. The experiments with this tube are described in Poggen- 

 dorffs Annalen, vol. xcviii. p. 487, 1856. Subsequently Dr. Geissler in Bonn 

 constructed his various well-known and beautiful tubes. This tube contains 

 a little mercury and carbonic oxide gas. 



1377a, Pour Geissler's Vacuum Tubes. E. Cetti and Co. 



1377b. Collection of Geissler's Tubes. 



Dr. H. Geissler, Bonn. 



1377c. Tube, by Geissler, for two gases. 

 Tube, by Geissler, forming a diadem. 

 Tube, by Geissler, forming a diadem. 

 Tube, by Geissler, with inner spiral. 



Tube, for liquids, with six spirals. 



Alvergniat Freres, Paris. 



1377d. Three Vacuum Tubes, to show the connexion 

 between the resistance of rarefied air and the phenomenon at the 

 cathode, the so-called negative glow. Prof. Hittorf, Munster. 



Apparatus (A) made by Dr. Geissler, of Bonn, consists of two balls which 

 communicate together by two tubes of equal width, one short and one of 

 spiral form 3| metres long. The electrodes of aluminium wire pass through 

 the balls and end in the short tube so that there is a free interval of only 

 2 mm. between them. The opening current of the Rhumkorff coil passes, in 

 consequence of the great rarefaction of the air in the tube, not by this short 

 path, but prefers the longer one. If the latter be stopped by closing the 

 glass cock, the passage is effected, but only at much greater tension, by 

 the short path. The tube (B) has the same arrangement, but without the 

 glass cock. It is used in place of (A) where the air is able to penetrate and 

 the required vacuum ceases. The glass vessel (C) consists of a wide reservoir 

 and a cylindrical tube, each of which holds one of the two equally long wires 

 as electrodes. The tension of electricity with which passage occurs is much 

 greater when the wire in the narrow part serves as cathode than when it is 

 anode. This may be shown if a spark micrometer be introduced in the induc- 

 tion current near the tube, and for each of the two directions the interval of 

 the balls be determined with which the current takes the path through the 

 tube. If the wire in the wide reservoir, being cathode, be placed in conductive 

 connexion with the third aluminium wire, which is in the beginning of the 

 cylindrical tube, the current can no longer pass over in the latter to the former 

 This, therefore, loses its negative light, and only with the greater tension, 

 such as occurs with the other direction, is the passage of electricity effected. 

 (Cf. Pogg. Ann., Bd. 136, p. 197.) 



