On tJie Action of the Magnet upon the Electrical Discharge. 119 



doctrine of derivation evidently conducts to a new branch of the 

 grand doctrine of invariance. I hope to have tranquillity of mind 

 ere long to give to the world my memoir, or a fragment of it, 

 "On an Arithmetical Theory of homogeneous and the Cubic 

 Forms/' the germ of which, now, alas ! many weary years ago, 

 fii'st dawned upon my mind on the summit of the Righi, 

 during; a vacation ramble. 



XIV. On the Action of the Magnet upon the Electrical Dis- 

 charge in Rarefied Gases. By M. Plucker*. 

 [With a Plate.] 

 1. rilHE idea of employing tubes with platinum electrodes 

 A fused into them for observing the electrical discharge 

 through rarefied gases, instead of the electrical egg, as originally 

 employed by Ruhmkorff and Quet, may be considered in many 

 respects a happy one. Such tubes, containing various gases and 

 vapours, are prepared in this city, of the most different forms, by 

 M. Geissler, and present sometimes an appearance of incom- 

 parable beauty. Geissler's tubes (I give them, and with justice, 

 this name, although the first such tubes were not prepared by 

 him) were tried at the beginning of this year in the Physical 

 Cabinet : and what more natural than the thought of approxi- 

 mating such tubes in various ways to the poles of a magnet 

 during the discharge ? Davy had already noticed that the arch 

 of light which he formed between carbon-points by means of a 

 powerful battery was diverted by the magnet. Arago had pre- 

 dicted such diversion. In the same way it was possible to pre- 

 dict generally the nature of the diversion of the electric current in 

 Geissler's tubes. But on the actual performance of the experi- 

 ment, in addition to the phsenomena which were looked for, 

 certain unexpected ones presented themselves ; namely, the divi- 

 sion of the light-stream, its decomposition at the negative elec- 

 trode into an undulating flickering light, and the extension of 

 the stream from the positive electrode into a bi-illlantly illu- 

 minating fine point. I communicated these results to the 

 Ilhcinische Gesellschaft der Naturforscher und Aerzte {Kolnische 

 Zeilung, July 22, 1857). I showed the phsenomena in question to 

 the members of this Society, as also afterwards to a section of the 

 Thirty-third Versammlung deutscher Naturforscher und Aerzte. 

 Soon afterwards, however, I was convinced that phaenomena of 

 the most beautiful kind, and such as were hitherto without 

 analogous ones, had remained unnoticed. This circumstance 



* Translated by Dr. F. Guthrie, from Poggendorflf's Annalen, vol. ciii. 

 No. 1, 1858, p. 88. 



