( '12) 



c'uiTeiits, the sensitiveness tbr <i qnicicly passed small qiianlily of 

 clectricit}' remains nearly iinallercd. 



And the practical application lies at hand. Whenever i-apid varia- 

 tions in electric tension have to be discovered and the distnrhance 

 by slowly varying currents has to be avoided, a rerpiiremeid whicii 

 frequently inqioses itself in ele('tr()-[)liysiol()i;ical iiiNestigations, the wire 

 must be relati^•ely strongly stretched. 



The described sensiti\eness for small aiid quickly passing quan- 

 tities of electricity, more even than its sensitiveness for constant 

 currents, makes the wire-galvauouielor a suitable reseairli-iu^trument 

 for a number of phenomena \\ liicli arc usually obserx cd by means of 

 an electrometer. 



If one end of the wire is earthed, the other Joiu'^d to an insulated 

 conductor, e.g. a resistance-box, a rubbed ebonite I'od. broiinlit U(?ar 

 the resistance-box, will act by influeiu'(^ and easily dri\e the image 

 from the scale. A single advam-ing or receding movement of the rod 

 must obviously result in a double movement of the wire, since this 

 latter alwa\s returns to zero when the rod stops moxing. At a distance 

 of a few metres, rubbing the rod ^vitll a silk cloth will still cause 

 deviations of the galvanometei-, each single stroke of the hand occa- 

 sioning a to and fro movement of the wire. 



When 1 had laid aside the eboinle rod and the silk cloth and 

 came near the resistance-box with the hand only, a small dellection 

 of a few ndllimetres could still be observed. When quickly approach- 

 in"' the hand, the wire showed a momentary deviation in one 

 direction, Avhen (juickl^ withdra^ving it, in the opposite sense. Even 

 moving the lingers round one of the plugs of the resistance-box 

 caused the wire to move. It must be emphasised that the resistance- 

 box was not touched l)v the haiul so that ordinary conduction 

 from the body through the galvanometer to the earth was out of 

 the question. 



I could not at once explain the phenomenon. My first thought was 

 that the body or at any rate the hand was charged to a certain 

 potential and like the ebonite rod drove electricity by intluence 

 through the resistance-box and the galvanometer. But the potential 

 of one of the hands of an uninsulated jjcrson is too small to explain 

 the movement of the wire. 



Also clothing, e. g. a woollen sleeve, appeared to [)lay no part, 

 If a round metal disk connected to the earth by a conducting wire 

 and hence having presumably the same potential as the galvanometer 

 and the resistance-box, was suddenly brought near or removed from 



