VOLTAIC INDUCTOR. 91 



meter was not considered capable of indicating the 

 passage of static electricity. The phenomena on longer 

 well insulated lines soon however rendered it quite 

 indubitable to me that it was a case of electrostatic 

 charge and not of polarisation. 



The first difficulty, the finding defective insulat- 

 ing points in a long piece of the conducting wire. I 

 was able to overcome in the following manner. The 

 dry wire coated with gutta-percha was drawn through 

 a vessel filled with water and insulated in respect to 

 the earth, whilst the second coil of thin covered 

 wire, which surrounded the electro -magnet of a Neef 

 hammer, was interposed between the insulated copper 

 wire and the earth. If now a workman standing in 

 communication with the earth dipped a finger into the 

 water of the insulated vessel, he felt electrical shocks 

 at the moment at which a defective piece of the wire 

 enveloped by gutta - percha was immersed. In this 

 wav I succeeded in detecting all the small defects of 



V 



insulation discoverable in no other way, and in obtain- 

 ing after their removal conductors with extremely 

 good insulation. 



With regard to the modification just described of 

 the Xeef hammer the following observation may here 

 find a place. I had already made this modification in 

 the year 1844 and given it the name of the voltaic 

 inductor. It even then afforded me the opportunity of 

 observing the therapeutic [effect of the variable currents 

 induced in the second coil of such a voltaic inductor. 

 My brother Frederick at that time was suffering a 



