ELECTRICITY 69 



attract nor repel it can not, because it is half way between 

 the two ends. But now, if I break out that piece (n, s), and 

 then examine it, see how strongly one end (n) pulls at this 

 end (S, FIG. 38), and how it repels the other end (N). And 

 so it can be shown that every part of the magnet contains 

 this power of attraction and repulsion, but that the power is 

 only rendered evident at the end of the mass. You will un- 

 derstand all this in a little while ; but what you have now to 

 consider is that every part of this steel is in itself a magnet. 

 Here is a little fragment which I have broken out of the very 

 centre of the bar, and you will still see that one end is at- 

 tractive and the other is repulsive. Now is not this power a 

 most wonderful thing? And very strange, the means of tak- 

 ing it from one substance and bringing it to other matters. 

 I can not make a piece of iron or any thing else heavier or 

 lighter than it is ; its cohesive power it must and does have ; 

 but, as you have seen by these experiments, we can add or 

 subtract this power of magnetism, and almost do as we like 

 with it. 



And now we will return for a short time to the subject 

 treated of at the commencement of this lecture. You see 



FIG. 41 



here (FiG. 41) a large machine arranged for the purpose of 

 rubbing glass with silk, and for obtaining the power called 

 electricity; and the moment the handle of the machine is 

 turned a certain amount of electricity is evolved, as you will 

 see by the rise of the little straw indicator (at A). Now I 



