401 



the galvanometer receded, the glow on the negative remaining more 

 or less brilliant ; 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 lamp was applied or withdrawn from the potash.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. 



1HH 



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. 





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. 



No. 187 was then replaced in the circuit, and the same phenomena, 

 as already described, were obtained. 



I now again avail myself of Dr. Robinson's notes of the experi- 

 ments made on the 5th of August. Tube 190 is of the same dimen- 

 sions as 187 and 196; but instead of the coke balls, it has brass 

 wires attached to the platinum. In this tube (190) the luminous 

 discharge did not appear until the caustic potassa was heated, when 

 most dazzling strata were observed. Dr. Robinson says, " I had 



