392 OBSERVATIONS AND EXPERIMENTS 



very fine platinum wires in a guttapercha column, out of which 

 copper wires connected with them projected. I cut through the 

 column vertically to the wires, which now appeared as two platinum 

 points at a distance of 2-5 mm. on the cut surface, moistened the 

 surface with the liquids used by John Davy sulphuric acid 

 (SO 4 H 2 : H 2 O : : I : i) and saturated solution of common salt and 

 observed the platinum points with a suitable magnifier. A single 

 discharge of the induction apparatus developed bubbles at the nega- 

 tive point ; but all efforts to get the same result with the shock of 

 the fish failed. I succeeded just as little in observing a deposit of 

 copper from a sulphate of copper solution on the negative electrode. 

 I might have tried to replace the positive point by a plate, but I 

 did not do so. 



2. Relation of the shock of Malapterurus to resistances 

 opposed to it. Its striking distance. 



The attempt failed completely to conduct the discharge through 

 two copper plates 75 mm. long, 40 mm. broad, which stood opposite 

 each other at a distance of 13 mm. in the flame of a Berzelius' 

 lamp ; in the experiment, Hankel's flame-currents showed them- 

 selves in the galvanometer *. 



I never succeeded in seeing the discharge pass over the smallest 

 gap between stationary metallic conductors with the formation of a 

 spark. I was indebted to the kindness of my friends, Messrs. 

 Siemens and Halske, for a spark-micrometer, in which I could 

 make two platinum points approach each other up to o-oioo mm. ; 

 I also made slits with a knife in strips of tinfoil stuck on microscope 

 slides, which were not wider than 0-0033 0-0050 mm. I never 

 succeeded, whilst observing with the microscope in the dark, 'in 

 getting a spark from the Malapterurus. 



On the other hand, I found to my surprise, that the secondary 

 current of the induction apparatus passed over this slit with forma- 

 tion of sparks, even when the secondary coil was at 90 mm. distance 

 from the primary coil. But my surprise increased still more, when 

 it was found that these discharges caused no sensation either 

 between handle-electrodes, or even on the tongue, although the 

 sparks continued to appear. Even gastrocnemius muscles in the 



1 Poggendorffs Annalen, etc., 1850, vol. Ixxxi. p. 213 : Elektrischen Unter- 

 suchungen, Ueber das Verhalten der Weingeistflamme in elektrischer Beziehung. 

 (Aus den Abth. d. math.-phya. Classe d. Kgl. Sachsischen Gesellschaft d. Wiss.)- 

 Leipzig, 1859. 



