150 DOVE ON THE ELECTRICITY OF INDUCTION. 



to the middle of the cylinders, the iron wires must lie symmetri- 

 cally in relation to the axis of the wire coil, they must therefore 

 once for all be fixed. This is effected by wooden frames and 

 brass holders, of each of which there were one cut open longitu- 

 dinally, the other entire. 



There were nine such pieces filled with wires, from 44 to 310 

 in number, the latter with a paper covering, the wires of which 

 were held together by lac. All the iron wires were varnished 

 to ensure more perfect insulation. 



61. The final result of a very extensive series of experiments 

 instituted with this apparatus was, that in relation to physiolo- 

 gical action, heating an electrical thermometer, deflection of the 

 galvanometer needle, magnetization of soft iron, chemical decom- 

 position and production of sparks, the solid cylinders over- 

 power the bundles of iron wires. If a bundle of wires opposes 

 in the one coil a solid cylinder in the other, an addition to the 

 number of wires constantly decreases the intensity of the shocks. 

 The experimerdum crucis in this department is this : two similar 

 bundles of iron wires, the one in an entire, the other in a longitu- 

 dinally cut tube, retain each other in complete physiological 

 equilibrium when connexion is made by the handles with dry 

 hands. The very slight action which is perceptible with wet 

 hands arises from the current directly induced in the wire coils 

 by appi'oaching them to the steel magnet, exciting a secondary 

 current in the enclosing case ; it is therefore perceptible when no 

 bundles of iron wires are inserted into the compensating wire 

 coils, and is not to be compared to the powerful differences 

 which are obtained with electro-magnetized bundles of wire 

 which are unenclosed or inserted in cases. The currents in- 

 duced by direct magnetization of the iron differ therefore from 

 those excited by electro-magnetization of the iron by a want of 

 those characteristic properties, which in these latter can be ex- 

 plained by the simultaneous excitation of electric currents ir 

 the iron. 



[To be continued.] 





