DOVE ON THE ELECTRICITY OF INDUCTION. 115 



previously been sepai'ated, that the current of one spiral passed 

 through the 100 revolutions of one wire of the galvanometer in 

 an opposite direction, to the current of the other spiral which 

 passed through the 100 revolutions of the other wire ; when 

 equilibrium had been established for the astatic needle between 

 the solid cylinder and the bundle of wires, the force of the shocks 

 in both the separated spirals was tested, and those produced by 

 the bundle of wires were found to be decidedly stronger. 



10. Although we have here direct proof (for the currents in 

 the foregoing experinients always circulated in the same wire) 

 that the non-existence of equilibrium for sensation, when the 

 human body is interposed in that current which produces no do- 

 flection of the galvanometer, cannot be accounted for by an in- 

 crease in the resistance to conduction, nevertheless, as a more 

 rigid test, the following experiment was made. The induction- 

 spirals were increased in length to 300 feet, so that the currents 

 having opposite directions, passed altogether through 400 feet of 

 wire. Afterwards 2000 feet of wire, and again much greater 

 lengths of wire were interposed, without in the least disturbing 

 the equilibrium in the galvanometer. A great increase of the 

 resistance to conduction was therefore without effect. 



11. The results obtained for iron appeared also to be appli- 

 cable to nickel. A fom*- sided rod of nickel, which was compen- 

 sated as regarded sensation by iron wires, produced in the gal- 

 vanometer a deflection in the direction of the current from 

 the rod. 



12. With regard to the galvanometric equilibrium, a remark- 

 able phaenomenon must be mentioned, which indicates that the 

 augmentation of the currents to the maximum of their intensity 

 with the same mean power does not take place in the same time. 

 Suppose the number of the wires to overpower the solid 

 cylinder, so that the deflection of the needle is in the direction 

 of the current produced by the wires, and that this excess is 

 lessened by the gradual removal of wires, then the deflection is 

 not observed to pass through the point of equilibrium, by gradu- 

 ally decreasing deviations, into one of an opposite direction, but 

 the needle moves, as if driven by a quick, short impulse, in the 

 direction of the former deviation, then suddenly stops, and re- 

 turns much more slowly in the direction of the other current. 

 This vibratory motion is still observed when the second current 

 has become the more powerful, so that the short impulse in the 



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