666 HENRY A. ROWLAND 



the wire, the north pole tending to revolve around it in one direction 

 and the south pole in the other. This is a very old experiment, but we 

 now regard it as evidence that the properties of the space around the wire 

 have been altered rather than that the wire acts on the magnet from a 

 distance. 



Put, now, a plate of glass around the wire, the latter being vertical 

 and the former with its plane horizontal, and pass a powerful current 

 through the wire. On now sprinkling iron filings on the plate, they 

 arrange themselves in circles around the wire and thus point out to us 

 the celebrated lines of magnetic force of Faraday. Using two wires 

 with currents in the same direction we get these other curves, and, test- 

 ing the forces acting on the wire, we find that they are trying to move 

 towards each other. 



Again, pass the currents in the opposite directions and we get these 

 other curves and the currents repel each other. If we assume that the 

 lines of force are like rubber bands, which tend to shorten in the direc- 

 tion of their length and repel each other sideways, Faraday and Maxwell 

 have shown that all magnetic attraction and repulsions are explained. 

 The property which the presence of the electric current has conferred on 

 the luminiferous ether is then one by which it tends to shorten in one 

 direction and spread out in the other two directions. 



We have thus done away with action at a distance, and have account- 

 ed for magnetic attraction by a change in the intervening medium as 

 Faraday partly did almost fifty years ago. For this change in the sur- 

 rounding medium is as much a part of the electric current as any thing 

 that goes on within the wire. 



To illustrate this tension along the lines of force, I have constructed 

 this model, which represents the section of a coil of wire with a bar of 

 iron within it. The rubber bands represent the lines of force which pass 

 around the coil and through the iron bar, as they have an easier passage 

 through the iron than the air. As we draw the bar down and let it go, 

 you see that it is drawn upward and oscillates around its position of 

 equilibrium until friction brings it to rest. Here, again, I have a coil 

 of wire with an iron bar within it with one end resting on the floor. 

 As we pass the current and the lines of magnetic force form around 

 the coil and pass through the iron, it is lifted upwards although if 

 weighs 24 pounds and oscillates around its position of equilibrium 

 exactly the same as though it were sustained by rubber bands as 

 in the model. The rubber bands in this case are invisible to our 

 eye, but our mental vision pictures them to us as lines of magnetic 



