Prof. Waltenhofen on an anomalous Magnetizing of Iron. 115 



to the original position of equilibrium ; in the second case, on 

 the other hand, the rapidity of the retrograde movement — in 

 proportion to the greater vis viva which the molecules acquire on 

 the sudden removal of the state of tension— carries them still 

 further back towards the original position of equilibrium, and in 

 many instances even overstepping of this original position of 

 equilibrium may occur. When the latter takes place, then the 

 further possibility arises that a number of magnetic particles 

 may remain permanently beyond the original position of equili- 

 brium, and then a magnetic condition of an opposite kind to 

 that set up by the electric current may be produced. A needle 

 the oscillation of which is retarded by considerable friction, will, 

 on the sudden or gradual withdrawal of the magnetic tension, 

 behave so as to render the above description experimentally 

 intelligible. 



After these remarks, I will give the numerical data belonging 

 to some of the experiments. In giving numbers for magnetic 

 intensities, a moment of a million absolute units is always taken 

 for the unit. 



An absolutely unmagnetic cylinder of the softest iron, 103 

 millims. long, and 28 millims. in diameter, was magnetized ( — ) 

 with an increasing intensity of current, so far that its temporary 

 moment reached finally about 60. On suddenly stopping the 

 stream, it showed a residual magnetism —0*20, and on repeatedly 

 making a sudden break in the circuit, it showed a decidedly 

 negative residue. On the other hand, when the magnetizing 

 current was gradually stopped, a regular residue of at least 0*30 

 always appeared. When the current was again passed in the 

 same direction and suddenly stopped, then the residual magne- 

 tism, instead of being 0*30 as on gradually stopping, diminished 

 to about 0, but could not be brought below zero, even on 

 repeating the experiment. But on altering the direction of the 

 magnetizing current and then arresting it suddenly, a very 

 marked anomalous magnetizing showed itself; from which it 

 would seem that a bar of iron in which residual magnetism has 

 been once induced, suffers an anomalous overstepping of the 

 molecular equilibrium easier towards the side on which the 

 molecules have been turned by that former residual magnetism. 



As often as the iron cylinder was left undisturbed for several 

 days, lying east and west in a horizontal position, it became 

 again completely unmagnetic, and gave, on repeating the first- 

 mentioned experiment, the anomalous residue— 0*20, the tem- 

 porary magnetism which had disappeared having been 60; it 

 showed, in fine, the same character as when first used. If, on 

 the contrary, the magnetic residue had not been removed by 

 long rest, but had been neutralized by means of opposite cur- 



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