164 MM. Elster and Geitel On 



Thus the electromotive force (E) was determined as fol- 

 lows: — for 



millini. 

 ,s= 1 E = 104 



*=20 E = 104 



s — 60 E= 94 (wire at the extreme apex). 



Lastly, as a third noteworthy point may be added that the 

 electromotive force is independent of the size of the flame, and, 

 consequently, of the amount of the burning gas. This is evi- 

 dent from the following experiment: — 



By regulating the admission of the gas, over the same 

 aperture of the burner three flames of different height h were 

 produced, and their apices connected with the insulated pair 

 of quadrants by a clean plate of platinum. There were found, 

 for 



A = 20 A=35 A=70 



E = 73*7 E = 75 E = 73-l>, 



consequently the electromotive force E independent of the 

 height Ii of the flame. Two subsequent series of experiments 

 gave the same result. Here the arrangement of the experi- 

 ment was that shown in fig. 2 a. 





1st series. 



2nd series. 



A = 20 



E = 142 



E = 213-2 



A =40 



E = 145 



E = 219-2 



/i = 70 



E = 142 



E = 216-0 



The reason of the value of E being here so much higher will 

 appear subsequently. 



§ 4. Polarization of the Flame in the Cross Section. 

 If the flame were polarized lengthwise, the surfaces of equal 

 potential would be given by planes perpendicular to the axis 

 of the flame. On examining cross sections of this sort, the 

 surprising result was obtained that, if the two platinum wires 

 laterally introduced penetrate the flame to an equal depth, the 

 difference of potential within one and the same cross section 

 = 0, but that with a slight horizontal displacement of either 

 electrode a difference of potential often appears, which equals 

 that produced by the vertical displacement or far exceeds it. 

 The latter takes place whenever one of the electrodes no longer 

 dips into the flame, but into the enveloping shell of hot air 

 (A A', fig. 1). The layer of air immediately enveloping the 

 flame plays therefore an essential part in the electrical be- 

 haviour of the flame. 



