446 Prof. E. Edlund on the least Electromotive Force 

 gave a deflection of 34°. For the same intensity we have : — 

 The length of the arc =4 divisions, its resistance =11*0 

 )> » == 4 }) a = 9*5 



From this we have ff = 8*0, and 5 = 0*75. 

 The electromotive force and the resistance were measured 

 anew; the first was E = 15*34, and the latter M = 8*51. The 

 mean in this experiment was M = 8*04, and E = 14*41. From 

 this we may calculate 



D=£^- xE=0'38E = 5-48.- 



Experiment 10. — Twenty-five elements of the battery were 

 used, which gave a distinct luminous arc. M was found =2*55, 

 and E = 5-49. 



Experiment 11. — The battery consisted of twenty elements, 

 but no luminous arc could be produced by them. M was found 

 on measurement =1'99, and E=4 e 23. 



Fourth Series. 



Copper wires were used for pole-points. 



Experiment 12. — The battery consisted of sixty elements. The 

 electromotive force was 16*35, and the resistance M = 8*45. 



When 2 inches of the rheostat were introduced into the cir- 

 cuit and the length of the luminous arc was four divisions, the 

 deflection on the tangent-compass was 46° 30'. With the same 

 intensity there was obtained :— 



Length of the arc 4 divisions, its resistance =4*9 



a )> & )> )) =4'D 



From this we have & = 4*3, and Z>=0 , 15. 



The electromotive force and the resistance were next mea- 

 sured, and gave M = 9 # 84, and E = 1 7*83. The mean of this ex- 

 periment was therefore M = 9*14, and E = 17*09. 



From this we find that 



D= tl^r xE = 0*268E = 4*58. 

 16*04 



Experiment 13. — The battery consisted of twenty elements, 

 with which a distinct luminous arc was obtained. M was here 

 = 1*56, and E = 4*65. 



Experiment 14. — With the fifteen elements of which the bat- 

 tery consisted, no luminous arc could be produced. M was 

 found, on measurement, to be 1*30, and E = 2*98. 



Experiment 15. — This was made with twenty elements, a few 

 days after the latter, and a distinct luminous arc obtained. On 

 measuring, E was found =3*51, and M = l*23. 



