34 FARADAY 



distances. I showed you the electric attraction on the last 

 occasion (though I did not call it so) ; that attracts 

 at a distance; and in order to make our progress a 

 little more gradual, suppose I take a few iron particles [drop- 

 ping some small fragments of iron on the table]. There! 

 I have already told you that in all cases where bodies 

 fall it is the particles that are attracted. You may con- 

 sider these, then, as separate particles magnified, so as 

 to be evident to your sight ; they are loose from each other 

 they all gravitate they all fall to the earth for the force 

 of gravitation never fails. Now I have here a centre of 

 power which I will not name at present, and when these 

 particles are placed upon it, see what an attraction they have 

 for each other. 



Here I have an arch of iron filings (FiG. 12) regularly 

 built up like an iron bridge, because I have put them within 

 a sphere of action which will cause 

 them to attract each other. See! I 

 could let a mouse run through it; and 

 yet, if I try to do the same thing 

 with them here [on the table], they 

 do not attract each other at all. It 

 is that [the magnet] which makes 





them hold together. Now just as 



these iron particles hold together in 

 the form of an elliptical bridge, so 

 FIG ia do the different particles of iron 



which constitute this nail hold to- 

 gether and make it one. And here is a bar of iron; 

 why, it is only because the different parts of this iron 

 are so wrought as to keep close together by the attrac- 

 tion between the particles that it is held together in one 

 mass. It is kept together, in fact, merely by the attraction 

 of one particle to another, and that is the point I want 

 now to illustrate. If I take a piece of flint, and strike it 

 with a hammer, and break it thus [breaking off a piece of 

 the flint], I have done nothing more than separate the par- 

 ticles which compose these two pieces so far apart that their 

 attraction is too weak to cause them to hold together, and 

 it is only for that reason that there are now two pieces in 



