80 Intelligence and Miscellaneous Articles. 



A second tube of the same length, of a spherical form in the 

 middle and with conical prolongations at the two ends, presented the 

 same phrenomenon at the negative pole ; but in the light of the 

 positive pole, independently of the streaks previously indicated, there 

 were two small dark streaks in the blue. 



The wires soldered into the glass tubes were of platinum. In the 

 cylindrical electrical egg with brass electrodes, tlae phsenomena are 

 the same as in these tubes, with this diiferencc only, that the ne- 

 gative light between the two broad black bands appears greenish, 

 nearly like the space between F and h in the solar spectrum, and 

 that in the spectrum of the positive light, besides the bands in the 

 red and green, several also make their appearance in the blue. 



If the point at the negative pole be replaced by a ball, the 

 positive pole remaining the same as before, there appears in the red 

 of the negative light a small dark streak, whilst in the positive light 

 two strong dark streaks become visible in the blue. Thus the phse- 

 nomenon becomes modified, as if each of the two lights, positive and 

 negative, contained a slight proportion of the other. In every case 

 the spectra remain different, of which it is very easy to con- 

 vince oneself, when the fissure is long enough to allow the two 

 spectra to be observed at the moment when the prolongation of the 

 one penetrates into the other. 



To observe the spectrum of the spark, the points of a spark-micro- 

 meter were placed in communication by a thread of glass, and in 

 this way a stream of sparks was obtained, in the light of which the 

 characteristic brilliant streaks were strongly marked. 



Non-continuous spectra, such as those above described, are pro- 

 duced by coloured flames, or wlien a source of white light is sub- 

 mitted to the absorption of coloured gases. Now, as the space Avhich 

 separates the poles is not an absolute vacuum, we may suppose that 

 various gaseous matters, or a single gas in different states, occur at 

 these poles. The two cases suppose, it is true, a certain duration 

 in the action of the pole and an action which increases with this dura- 

 tion. If we introduce a commutator between the pile and the Ruhm- 

 korfF's apparatus, the two spectra immediately change, and remain 

 without alteration, which is contrary to the hypothesis in question. 



When the luminous current is deflected by means of a strong mag- 

 net, no change is observed in the spectra. 



The luminous phrenomena presented by electricity in vacuo exhibit 

 a striking analogy with those of the aurora borealis, which has caused 

 them to receive the name of artificial aurorre boreales. The fiery red 

 of the positive pole particularly resembles the red which characterizes 

 many auroras , and the author has of late years repeatedly had the 

 opportunity of remarking this resemblance, especially in two cases of 

 aurora borealis seen at Berlin. The peculiarities presented by the 

 electric light bi vacuo are so marked, that it ai)j)cars easy to decide 

 definitively by prismatic analysis whether the light of the aurora 

 borealis is or is not of an electrical nature. --Poggendorff's Annalen, 

 1858, No. 5. 



