648 HENRY A. KOWLAND 



a magnet, and how we are able to measure them by the induced current 

 in moving wires. The method of exploring the magnetic field is the only 

 exact method which has ever been devised for use in such cases as the 

 field of modern dynamo-electric machines, or in most of the problems 

 of modern electrical engineering. He also proved that the lines of in- 

 duction are always closed circuits, whether they are due to permanent 

 magnets or electric currents, thus forever destroying our hope of obtain- 

 ing a continuous current by induction without the use of a commutator. 



When a soft iron bar was approached to the magnet, it drew the lines 

 in upon itself; they proceeded down the bar until they were forced into 

 the badly conducting air and the number which went further down the 

 bar to those which passed out into the air at any point was in proportion 

 to the conductivity of the two. A steel magnet was, in his eyes, like a 

 voltaic pile in water. As the current of electricity was forced forward 

 by the electromotive force of the pile and diffused itself in currents 

 through the water, so the lines of magnetic induction were formed by 

 the coercive power of the steel. It is now known to be a fact that the 

 distribution of magnetism on a steel magnet, or indeed in any case, can 

 be calculated by these principles Faraday laid down. The idea of a mag- 

 netic circuit is familiar now to all electrical engineers. 



To Faraday's eye, a magnet not only consisted of a piece of steel or 

 loadstone which is apparent to our ordinary vision, but included all the 

 space around which was filled with lines of force; it was bounded only by 

 the limits of the universe. The steel served merely to bind together 

 the ring-like lines of induction which passed from the magnet to every 

 point of space. 



Faraday was not a mathematician, and could not thus follow out the 

 consequences of his great ideas. This has been done for him by the im- 

 mortal Maxwell. He has taken up the idea that electrical and mag- 

 netic forces only proceed to a distance by aid of the intervening particles 

 of matter, or ether, as the case may be, and has given it a mathematical 

 basis. 



To-day a body charged with electricity, a magnet or a wire carrying 

 an electrical current, all are incomplete without the space around them. 



When we attach a battery to a wire and the current apparently flows 

 through it as if it were a current of water, Faraday's idea shows us that 

 we are only looking at the matter superficially; around that wire and 

 permeating space in every part are lines of magnetic force, and lines of 

 electrostatic force. At the moment of joining the battery to the wire 

 this whole complicated system of lines of force must be formed. At the 



