DOVE ON THE ELECTRICITY OF INDUCTION. I7I 



are connected by means of handles through the human body, 

 the shocks are weaker with inserted spirals than without them, 

 the reason of which is obvious. But this physiological action 

 is weakened still more by the insertion of unenclosed bundles of 

 iron wire and tubes of sheet iron into the spirals ; it is not so 

 much weakened by the insertion of iron bundles of wire in entire 

 tubes, solid rods of soft iron, of soft and hard steel, of cast 

 iron and nickel ; the action remains nearly the same as with in- 

 serted empty spirals, when the inserted rods are composed of 

 copper, zinc, tin, brass, bismuth, antimony, or of the so-called 

 unmagnetic metals in general. All these phaenomena remain 

 unaltered when the spirals are connected in a like or in an alter- 

 nating manner. The facts here adduced therefore, indicate the 

 existence of an extra current in an opposite direciion to the 

 primary current ; and moreover, no difference is perceptible in 

 this action whether the primary current is continuous in the same 

 direction, or Avhether it is alternating. 



73. If the weakening of the physiological action here observed 

 is to be attributed to an extra current circulating in an opposite 

 direction, then this weakening influence must be very much di- 

 minished when the extra spiral is allowed to exert an inducing 

 action upon a secondary wire placed parallel to it. To test this, 

 a narrower extra spiral having 400' of wire was inserted between 

 the clamps 1) and 6), and this spiral itself was inserted into a 

 spiral which may be called the secondary spiral, likewise consist- 

 ing of 400' of wire. When a bundle of iron wires or a solid 

 iron rod was now placed into the extra spiral, the shocks from 

 the handles I and III were verj^ inconsiderable as long as the 

 outer secondary spiral was not closed, that is, as long as no se- 

 condary current could be produced in it. A.S soon however as 

 this secondary spiral was closed, and as soon as the secondary 

 current could be made manifest in it by any of the modes of 

 testing, then the shocks from the handles I and III again be- 

 came powerful. Two extra spirals each 400' in length were now 

 inserted between the clamps 1) and 6), and upon each of these 

 again a secondary spiral, likewise 400' in length. By a trans- 

 verse connexion of these secondary spirals, the induced se- 

 condary currents neutralized each other, not however when the 

 connexion was in a like direction. The shocks in the handles I 

 and III were in the first case much more powerful than in the 



