358 Prof. E. Edlund on the New Electromotive 



to 5*67/3,, the entire resistance in the battery, in the rheostat, in 

 the arc, and in the magnetometer together amounts to 1093p. 



If the resistance in experiment 2, as in experiment 1, had 

 been equal to 5'67p, the deflection of the magnetic needle must 

 have been 



— — — x 27-9 = 53-8 divisions, 

 o-y/ 



Hence we have 



53-8:18-7 = 50-^:^ 



from which x = 12*9 elements. 



Experiment 5. The battery consisted of fifty elements; and five 

 inches of the solution of sulphate of copper were introduced into the 

 circuit. The resistance of the battery was found to be 3'97p, which, 

 together with the resistance in the circuit, makes 6'4<p. When 

 the galvanometer circuit surrounded the luminous arc, the deflec- 

 tion on reversing the lever was 11 '7 divisions as the mean of ten 

 observations, with a probable error of +0*85. When thereupon 

 a resistance = 12'9p was introduced into the circuit, the deflec- 

 tion was equal to 6"5 divisions as the mean of ten observations, 

 with a probable error of + 037. From this it may be calculated 

 that the resistance in the luminous arc and the magnetometer 

 together was equal to 16'lp. The great increase in the resist- 

 ance of the luminous arc was probably due to a smaller intensity 

 of the current. 



Experiment 6. The battery and the interposed resistance were 

 the same as in experiment 5. The magnetometer-wire was con- 

 nected with the commutator and the principal circuit as repre- 

 sented in fig. 2. When the lever was reversed, a deflection was 

 always obtained amounting to 19'2 divisions as the mean of fif- 

 teen observations, with a probable error of +1'35. The resist- 

 ance in this case was = 22'5p ( = 6'4p-\- 16'lp). If the resist- 

 ance had been equal to 16'lp, as in experiment 5, the deflection 

 would have been =26'83 divisions. We have thus 



26-83: ll'7 = 50-x:x, 



from which #= 15-2 elements. 



Hence the mean of the three determinations adduced of the 

 electromotive force of the vanishing luminous arc amounts to 

 12*6 elements. The probable errors adduced above show that 

 this determination can lay claim to no great accuracy. It is 

 possible that the true value may be a few units above or below 

 the one adduced ; but this is immaterial for our immediate object. 

 The experiments adduced prove that, in the voltaic arc between 

 carbon points, during the first moment after extinction there is an 

 electromotive force comparable in magnitude to that of from ten to 



