by which a Galvanic Luminous Arc can be produced, 445 



was obtained with this. In these experiments M = 3'41, and 

 E = 7*20. 



Experiment 3. — Twenty-five elements. This occasionally gave 

 a distinct luminous arc. M = 2*96, and E = 6*00. 



Experiment 4. — Twenty elements. With these elements a 

 uminous arc could not be obtained, although the carbon-points 

 became strongly incandescent in the interval, which resembled a 

 true light. M = 2*58, and E = 4*60. 



Second Series. 



• 



The pole-points were of brass containing about 37 per cent. 

 of zinc. 



Experiment 5. — The battery consisted of sixty-six elements. 

 M = 9*25, and E = 17-26. 



When 1 inch of the rheostat was interposed and the length of 

 the arc was three divisions, the tangent-compass was at 52°. 

 With this intensity there was found : — 



The length of the arc 3 divisions, its resistance = 2*8 

 „ „ 2 „ „ = 2*6 



From this we obtain « = 2*2, and 5 = 0*2. 



Thereupon the resistance and the electromotive force were 

 again determined; they were found to beM== 10*71, andE== 18*57. 



The mean in these experiments was M = 9*98, and E = 17*92, 



From this we calculate 



D= ,-l^r xE = 0-1597E = 2-86. 



Experiment 6. — Twenty elements. With these we get a di- 

 stinct luminous arc. M = l*56, and E = 3*65. 



Experiment 7. — Fifteen elements. A distinct arc could be 

 obtained with this electromotive force. In these experiments 

 M = 0-84, andE = 2*65. 



Experiment 8. — In this experiment only ten elements were 

 used, and no arc could be produced by them. The resistance 

 and the electromotive force were measured, and were found to be 

 M = 0-32, and E = 1*60. 



Third Series. 



For the pole-points in this series, carbon was used which had 

 been sawn out of a piece of broken battery carbon. It appeared 

 to be softer than the carbon used in the first series. 



Experiment 9. — The battery consisted of sixty-six elements. 

 M was found =7'56, and E= 13*48. 



When 2 inches of the rheostat were brought into circuit and 

 a luminous arc of four divisions formed, the tangent-compass 



