50 Dr. von Feilitzsch on Magnetic and Diamiig'ketic Bodies. 



If the winding of the spiral took place in the direction of the 

 hand of a watch, then the end of it, where the current enters, 

 will become a south pole ; but a north pole, kept parallel to 

 the spiral, will repel it. Only the final convolution will be at- 

 tracted, and it represents the disengaged magnetism of the final 

 sui'face. 



A second spiral is wound like that described, only with this 

 difference, that the strongest convolutions are in the middle, and 

 the feeblest near the ends. This spiral will be attracted by the 

 north pole of a magnet over the half in which the current moves 

 at first, or enters, but the other half will be re])ulsed by it. The 

 third spiral has the windings the same strength over the whole 

 extent : it is indifferent to a magnet pole, which is not too near, 

 and only the final convolutions are attracted or repulsed. 



Therefore it is permitted to enlarge the theory of Ampere in 

 this manner : — 



If an electric current passes through a spiral in the direc- 

 tion of the hand of a watch, and 



a. If the current is more feeble in every winding, as it is 

 nearer to the centre of the spiral, then that half is at- 

 tracted by a south pole, in which the current enters, 

 except the first winding ; 



b. But if the current is stronger in every winding, as it is 

 nearer to the centre of the spiral, then that half is re- 

 pulsed by a south pole, in which the current enters, in- 

 cluding the first winding. 



The contrary will be the case for that half in which the current 

 leaves the helix, and likewise for the north pole of the magnet 

 opposed. 



With this extension of the theory of Ampere, it is easy to 

 apply it to the views above brought forward. In the mole- 

 cules of magnetic and diamagnetic bodies are electric ciuTents. 

 By the magnetism they will be in such a way directed, that they 

 put themselves parallel to the external acting currents. In the 

 diamagnetic bodies a very; great i-esistance is opposed to the 

 direction of these currents 6f the molecules, therefore their in- 

 tensity will decrease from the centre of the excitation. These 

 bodies will comply with the opinion that is given in a, they will 

 be repulsed. But in magnetic bodies the currents of the mo- 

 lecules that arc directed by external influence act on their part, 

 also directing the currents of neighbouring molecvdes, and in 

 such a manner that these currents are the most energetic in the 

 middle of the bar, but more feeble near the ends. These bodies 

 comply with the view given in b; they will be attracted, and 

 place themselves axial. 



