128 DOVE ON THE ELECTRICITY OF INDUCTION. 



opposite direction. Judging from this it must be immaterial, for 

 a certain given amount of polarity in the bundle of wires, what di- 

 rection is given to the coils of the enclosing spiral ; and this was 

 borne out by the experiments. The results were the following. 



32. If one of two bundles of wires, which compensate each 

 other when both are unenclosed, is placed within a uniformly 

 wound surrounding spiral with connected extremities, the gal- 

 vanometric action of the latter differs from that of the unen- 

 closed bundle, as does the action of a solid cylinder from that 

 of a bundle of wires. For whilst galvanonietric equilibrium is 

 hardly disturbed, those characteristic vibrations of the needle 

 occur which have already been mentioned, and the primary im- 

 pulse always occurs in the direction dependent upon the unen- 

 closed bundle of wires. The enclosing spiral, on the contrary, 

 weakens in an extraordinary manner the physiological effect, so 

 that a powerful shock is perceived arising from the unenclosed 

 bundle of wires. An entire brass tube enclosing the bundle of 

 wires presents analogous phasnomena to those produced by a wire 

 spiral with connected extremities ; a brass tube cut longitudi- 

 nally is however but little superior in power to a spiral with un- 

 connected ends. The existence of the electric current which is 

 on the point of being excited in such tubes can also be verified 

 by the galvanometer when it is made to connect the cut edges of 

 the tube. 



33. The property of magnetizing hard steel is in relation with 

 the physiological action of the current. Whilst seventy unen- 

 closed wires, acting in opposition to the solid cyhnder, magnetize 

 the steel needle in the direction of the cun*ent produced by 

 them, yet, when these wires are enclosed in an entire brass tube, 

 the magnetic excitation takes place in the direction of the cur- 

 rent produced by the soUd cylinder. The longitudinally cut 

 tube likewise diminished the magnetizing influence of the cur- 

 rent upon steel, probibly because, when it is filled with wires, 

 which partially close the section, peripherical currents are pro- 

 duced, although of a more imperfect kind. When the copper 

 spirals are exchanged for spirals of thin German-silver wire, and 

 the brass tube for one of German-silver, the retarding action of the 

 case is also diminished. When the bundles of wires are opposed 

 to each other, the one in a closed and the other in an open tube, 

 then in magnetizing steel the action of the open tube is more 

 powerful than that of the closed tube. 



