the Electricity of Flame. 183 



ourselves by numerous preliminary experiments), since the 

 two electrodes were metallically connected with one another 

 and with the earth before the flame was kindled. As the 

 shape of the small bluish flame was quite different from that 

 of a gas-flame in air, it was necessary to shift the base-elec- 

 trode somewhat, in order to attain an analogous position to 

 that in the first experiment. 



For the electromotive force of the 



Gas-flame in air, we found E = 148 

 Air-flame in gas, „ E = 152 



In both cases the glowing wire was negative, the not glowing 

 one positive, consequently the apparent polarity of the flame 

 the same. 



Lastly, another noteworthy circumstance should be men- 

 tioned: namely, the polarity of the air-flame appears reversed 

 when the flame-electrode is in the lowest and, therefore, cool- 

 est part and is not red-hot. We have seen, in § 13, that, with 

 aD analogous position of the electrodes in an ordinary flame, 

 the dark wire in the flame was always negative to one in hot 

 air. There we had the combination 



Platinum, Hot gas, Hot air, Platinum. 

 But with the air-flame we have 



Platinum, Hot air, Hot gas, Platinum, 



consequently the same elements in inverse order, from which 

 the reversal of the polarity of the flame results spontaneously, 



§ 16. Theory and Conclusions. 



On the basis of the above experiments the following theory 

 on the electricity of flame can be set up. 



By the process of combustion in itself free electricity within 

 the flame is not generated; on the other hand, the flame-gases 

 and the air stratum immediately enveloping the flame possess 

 the property, when in contact with metals or liquids, of exci- 

 ting it similarly to an electrolyte. To this electrolytic exci- 

 tation is added a thermoelectric excitation, produced by the 

 state of incandescence of the electrodes. The quantity and 

 kind of the electric excitation is then 



(1) Independent of the size of the flame; 



(2) Dependent on the nature, and the quality of the surface, 

 of the electrodes ; 



(3) Dependent on the nature of the combustion-gases ; 



(4) Dependent on the state of incandescence of the elec- 

 trodes. 



