Lecture on a new property of Magnetism. 53/ 



can soon test it. If I place a piece of copper wire — and all this 

 copper wire has been examined — and hang this up so that it shall 

 come between the poles of the magnet, and the thread is able to bear 

 it, I have no doubt that it will point. On making contact, it stops 

 the vibration. That slice of apple will vibrate about this line. It will 

 not pass beyond except from some gust of air. As long as it is ex- 

 posed to the magnet, it will point equatorially, or contrary to the 

 magnetic needle. It swings right and left ; it is a diamagnetic body 

 by virtue of the water and other principles it contains. I have tried 

 it over and over again : I have not tried asparagus, but will do so 

 now to point out to you and satisfy myself that these bodies are 

 diamagnetic, because it is an important point to us, or at least will 

 be so hereafter. This piece of asparagus will show for itself what 

 position it takes up in the magnetic field. It is only requisite that 

 we should take a longitudinal substance and then the thing points. 

 Making contact stops the action ; it went back when it came to this 

 line ; it will not go beyond it, but will take up this equatorial position. 

 I might put a mouse there, a flounder, or anything that is elongated 

 in this direction, and }^ou get the phenomena. You must have longi- 

 tudinal bodies to show this effect ; and you see how beautifully this 

 substance is vibrating across the magnetic force. 



I must occupy the rest of the time, the few moments that remain, 

 in speaking of the magnetism of the earth, which I fear is not 

 distinctly understood as it regards the nature of the lines of force, 

 and the condition of bodies on its surface. 



I have told you before that the earth is a magnet, and you know 

 it by the way in which a needle points upon the surface. Bat it is 

 not a magnet, like that needle. It is not as if we had a large 

 magnet extending from end to end from the south to the north poles 

 but it is more as if the magnetic force were something dependent on 

 the equator. I will build up an earth to show this. You must not 

 mind the form of apparatus I am about to use. Assuming this 

 bottle were the earth, making the neck the pole, then putting round 

 this earth of our' s currents of electricity, you see how differently they 

 come out to what they would do if they were suspended. Here is a 

 globe around which I can throw currents of electricity, which you 

 know are magnetic from the effects you have seen from this battery. 



4 A 



