332 



soon became heated by the discharge. As the discharge of the battery 

 continued, a sudden flash of light was visible in the vacuum, and the 

 glass instantly became coated with metal. On examining the tube, I 

 ascertained that one-half of the negative ball was separated from the 

 other, and partly fused : the intense heat had vaporized the silver 

 with which the two hemispheres forming the ball had been soldered, 

 and it was this vaporized metal that was deposited on the sides of 

 the tube. The positive ball remained much tarnished, as if it had also 

 been heated. 



11. I then introduced the second tube, having similar hollow 

 brass balls, into the circuit of the battery. In this tube the negative 

 also was at first heated to redness ; when in this state, a sudden bril- 

 liant stratified discharge took place, as fig. 5. 



Fig. 5. 

 + f i - 





The evolution of nitrous acid fumes in the battery denoted its in- 

 tense action. This discharge from the battery continued for about two 

 seconds, the negative ball instantly losing its luminosity, the positive 

 becoming red-hot. 



12. This experiment appeared to offer an explanation as to the 

 cause of the heating of the poles ; but on attempting to repeat it, the 

 tube was unfortunately fractured by the heating of the platinum wire, 

 as were also two tubes with coke balls : the result I had obtained was, 

 however, too interesting to me not to repeat the experiment ; and I 

 had six vacuum- tubes prepared, each of the same dimensions as 

 already described, two with coke balls, two with iron, and two with 

 copper, all solid : the best and most conclusive results were obtained 

 with the copper. The experiments which I now proceed to describe 

 were made on the 27th of last May, in the presence of the Rev. Dr. 

 Robinson and Professor Stokes. 



13. In the first tube the negative ball very soon became red-hot, 

 when suddenly the brilliant, clearly defined, conical stratified dis- 

 charge as in fig. 5 appeared, continuing for three or four seconds. 

 On breaking the circuit of the battery, we ascertained that the negative 

 ball, or that attached to the zinc terminal of the battery, had, as before, 

 entirely lost its heated appearance, while the positive, or that attached 



