M. E. Goldstein on Spectra of Gases. 345 



Some pages back I have spoken of a yellowish rosy part in the 

 negative half of many jars' sparks, which part gives a spectrum 

 continuous as far as the blue : the preceding lines might contain 

 an explanation of this phenomenon (at least with regard to the 

 spectral peculiarity). The outside appearance of it, that in 

 the spark there is a place of different colour and brightness, is 

 already known in principle by observations of machine-sparks 

 by Adams, Knoch, Dove, and others. I have seen similar phe- 

 nomena with induction-sparks in dense air. 



The spectrum of the blue light at the cathode has often been 

 discussed; upon another occasion I will communicate my expe- 

 riences in respect to this. Here I would only like to draw atten- 

 tion to the fact that colour and spectrum of this light are not 

 always identical. The changes mentioned are most striking 

 when the negative light appears with the optical properties of 

 the positive one. With high rarefaction the negative layers 

 situated from the second towards the outside adopt the colour 

 and spectrum of the positive light. 



With jar- discharges of greater intensity the total light near 

 the cathode cannot be distinguished, either by its colour or by 

 the prism, from that of the positive current. The tendency to 

 conform itself to the magnetic curves is then still evident. But 

 negative light can also appear far from the cathode. If tubes 

 like those used for spectral purposes, or many brought into trade 

 as effective articles, cylinders, balls, ellipsoids, are parted off, 

 then each one of these parts behaves during the discharge very 

 nearly like an independent tube having its electrodes at the 

 two entrance-points of the current. At the negative entrance- 

 point light shows itself, which by its straight-lined disper- 

 sion, the capacity to cause fluorescence, and the property of 

 conforming itself to the magnetic curves under the influence of 

 a magnet is characterized as negative light. Its form corre- 

 sponds to that light which would proceed from a cathode, the 

 surface of which would fill the entrance-point. The diffused 

 cloud of light which forms round such an electrode, which has 

 more or less the shape of a point, is represented with the newly 

 found appearance of negative light, by light almost of the 

 colour of the positive. In its spectrum, which on the whole 

 coincides with that of positive light, some maxima of the nega- 

 tive light seem certainly to be marked sharper than the corre- 

 sponding wave-lengths of positive light. To that cone which, 

 distinguished by brightness, stands perpendicular on the cathode 

 and forms the central axis of the phenomenon, here again a cone 

 corresponds of the colour of the negative light. 



I retain the details of this and other, simultaneous phenomena 

 for a future communication. 



