546 



Royal Society 



of light appeared on the positive (fig. 1 B), and the needle gradu- 

 ally deflected 40° or 50°. On withdrawing the lamp, as the potash 

 cooled, the positive glow disappeared, the needle of the galvano- 



Fig. 1 B. 



meter receded, the glow on the negative remaining more or less bril- 

 liant, — this action and reaction alternating as the heat of the lamp 

 was applied or withdrawn from the potash. 



When the heating of the potash was further increased, four or five 

 cloud-like and remarkably clear strata came out from the positive 

 (fig. 1 C) ; and these were quickly followed by a sudden discharge 



Fig. 1 C. 



+ I 



1- 



am 



of the most dazzling brightness, which remained for several seconds. 

 The stratifications, which were conical in shape, I have endeavoured, 

 although very faintly, to depict in fig. 1 D. The needle of the gal- 



Fig. 1 D. 



I- 



^*>» 



vanometerwas suddenly and violently deflected, striking with consider- 

 able force the two corks placed to protect it on the compass card. 

 At the instant this discharge took place, and not before, the leaves of 

 the electroscopes collapsed. This, with the intense chemical action ob- 

 servable in the battery, proved that the entire current was passing. 



The preceding experiment was repeated with tube No. 196, with 

 nearly the same results, the needle first deflecting 40° and then 80°. 

 On further heating the tube, the same sudden intense stratified light 

 appeared, after which the discharge ceased. 



