388 Mr. J. Brown o?i Helmholtz's Theorij of 



point of the funnel just under the surface of the water (" up "), 

 or within about 3 millim. of the lower mercury (" down "), 

 as follows : — 



Up 26 divisions. Down 23-5. Up 23-5. Down 23-5. 

 Up 23. 



The electromotive force is therefore not sensibly influenced 

 by the length of fall. 



The somewhat larger first deflexion is perhaps due to a 

 higher degree of oxidation on the lower mercury, afterwards 

 modified by the fresh drops falling on it. This effect is 

 marked when the lower mercury has only a small surface 

 more easily affected by the mixture of fresh mercury. 



14. To experiment on the current from this arrangement, 

 the same apparatus was used with the addition of a glass 

 tube of 7 millim. diameter,' open at the ends and fixed upright 

 in the glass jar, its lower end a few millim. above the resting 

 mercury. The point of the funnel was placed in this tube 

 just under the surface of the water, and the dropping and 

 resting mercury connected to the terminals of a reflecting- 

 galvanometer. The deflexion was 57 divisions. Lowering 

 the funnel through about 30 centim. increased this to 400 

 divisions. 



Decreasing the length of fall, therefore, increases instead 

 of decreasing the current, and the increase is due here to the 

 decreased resistance of the electrolyte, for when the narrow 

 tube was removed and the same experiment performed in a 

 wide vessel, the current did not sensibly vary, since the chief 

 resistance was then at the small surface of the drops as they 

 formed at the funnel-point. 



It was stated by Quincke* that "the strength of this 

 current decreases with increased resistance of the fluid," 

 though the experiment on which he appears to base the 

 conclusion may be open to another interpretation. 



The hypothesis that the current is in any way produced by 

 the carrying down of charges on or in the falling drops is 

 negatived also by several of Konig's experiments, where the 

 dro]:>ping mercury did not fall into the resting mercury in 

 connexion with the electrometer but into another part of the 

 apparatus f. 



I find also that when the resting and dropping mercury are 

 connected through a galvanometer, the current remains the 

 same whether the drops fall into the resting mercury or not, 

 provided they are formed in the electrolyte. 



* Pog'g. Ann. cliii. p. 203. 



+ Wied. Ann. xvi. p. 35 (1882). 



