the Electricity of Flame. 175 



with one position of the turn-plate the value of the potential 

 is + as, it will be converted into —x by rotating the turn -plate; 

 that is. the direction of the electrometer-deflection must be 

 right or left according to the position of the turn-plate W x . 



The circumstance here discussed, indeed, rendered a small 

 correction necessary. Assuming that the wire c would behave 

 like a platinum electrode introduced into the hot stratum of 

 air of a flame, we can denote the value of the potential upon 

 it by + e. To this value + e the value of the potential at the 

 point v will be added or subtracted from it, according to the 

 position of the turn-plate "\V 1# If we denote by s x and s 2 the 

 deflections of the electrometer corresponding to the two posi- 

 tions of the turn-plate, we have 



e+x=s lf e—i>:=>. : . 

 consequently- „ ,„ 



If the earth-conduction is brought, not to the point u, but, 

 say, to the point r, this method still remains applicable; only 

 now x frequently >e, which for the moment slightly disturbs 

 the clearness of the experiment. 



The result was now obtained that a platinum wire c, brought 

 near to the incandescent wire, received a powerful positive 

 charge, consequently behaved like the base-electrode of the 

 flame. The agreement goes so far that even the values of the 

 electromotive force lie within the same limits. Xay, the 

 analogy between the two phenomena is still closer; for nearly 

 all the experiments above given for the flame can be repeated 

 with such an incandescent wire. 



The electromotive force, besides depending on the distance 

 of the wire c from the wire a b, turns out to be dependent 

 on: — 1, the state of incandescence of the wire ab\ 2. the 

 quality of the surface of the wire c. 



The correctness of these propositions follows from the fol- 

 lowing Table, in which the numbers are, for clearness, reduced 

 to equal sensitiveness of the electrometer. (A double deflec- 

 tion of the daniell=100.) 



Table III. 

 Conduction to earth in the point r (fig. 4). 

 Position of the wire c. 



millim. above a b (fig. 4). 

 milliin. laterally from a b. 



Series 1 {a 



a 



>). Con 



x+e. 





r-e. 



+ 151-0 





-10-0 



+ 150-6 





-16-1 



+ 169-5 





+ 6-0 



+ 155-0 





— 3-0 



+ 163-9 





+ 0-8 



161-0") 

 166-7 U 

 163-5 J 

 158-01, 



163-1 p 



