Action of Magnets on Copper and good Conductors. 461 



magnetic power be developed whilst the bar is in a position 

 oblique to the axial and equatorial lines, the experimenter will 

 perceive the bar to be affected, but this will not be manifest 

 by any tendency of the bar to go to the equatorial line; on 

 the contrary, it will advance towards the axial position as if 

 it were magnetic. It will not however continue its course 

 until in that position, but, unlike any effect produced by mag- 

 netism, will stop short, and making no vibration beyond or 

 about a given point, will remain there coming at once to a 

 dead rest: and this it will do even though the bar by the ef- 

 fect of torsion or momentum was previously moving with a 

 force that would have caused it to make several gyrations. 

 This effect is in striking contrast with that which occurs when 

 antimony, bismuth, heavy glass, or other such bodies are em- 

 ployed, and it is equally removed from an ordinary magnetic 

 effect. 



2311. The position which the bar has taken up it retains 

 with a considerable degree of tenacity, provided the magnetic 

 force be continued. If pushed out of it, it does not return 

 into it, but takes up its new position in the same manner, and 

 holds it with the same stiffness; a push however, which would* 

 make the bar spin round several times if no magnetism were 

 present, will now not move it through more than 20° or 30°. 

 This is not the case with bismuth or heavy glass; they vibrate 

 freely in the magnetic field, and always return to the equato- 

 rial position. 



2312. The position taken up by the bar may be any posi- 

 tion. The bar is moved a little at the instant of superinducing 

 the magnetism, but allowing and providing for that, it may be 

 finally fixed in any position required. Even when swinging 

 with considerable power by torsion or momentum, it may be 

 caught and retained in any place the experimenter wishes. 



2313. There are two positions in which the bar may be 

 placed at the beginning of the experiment, from which the 

 magnetism does not move it, the equatorial and the axial po- 

 sitions. When the bar is nearly midway between these, it is 

 usually most strongly affected by the first action of the mag- 

 net, but the position of most effect varies with the form and 

 dimensions of the magnetic poles and of the bar. 



2314. If the centre of suspension of the bar be in the axial 

 line, but near to one of the poles, these movements occur well, 

 and are clear and distinct in their direction : if it be in the 

 equatorial line, but on one side of the axial line, they are mo- 

 dified, but in a manner which will easily be understood here- 

 after. 



2315. Having thus stated the effect of the supervention of 



