ELECTKICAL AND MAGNETIC DISCOVERIES OF FARADAY 647 



that all bodies were acted upon by magnetism and could be classified as 

 magnetic or diamagnetic. Magnetism now had a universal significance 

 as applying to all bodies. It was universal in its action, and all bodies 

 responded to it to some extent at least. Even gases were acted on by it, 

 and the oxygen of the air was found quite strongly magnetic. 



Quickly his mind seized another idea. , 



As the intense magnetism of iron, nickel and cobalt was destroyed by 

 heat, might it not b possible that all bodies should become magnetic 

 when cold? He carefully tried the experiment, but never was able to 

 find any effect with the means of producing cold at his command. 



In reading Faraday's papers we are surprised at the clearness with 

 which his laws are expressed. Although he naturally wished to bring 

 his lines of force into use in this case of diamagnetism, yet we now find 

 him making no use of them. His law says that magnetic substances in 

 the field of a magnet tend to the stronger part of the field, and the dia- 

 magnetic to the weaker, irrespective of the direction of the lines of 

 force. 



Bismuth he found the most strongly diamagnetic of all bodies. In 

 using a crystal of this substance instead of a bar, he found that it 

 would set itself in a magnetic field, even if this was uniform. On using 

 other substances he proved the general law that all crystals possessed 

 this property and he called it magne-crystallic force. 



The researches on diamagnetism and magne-crystallic force occupied 

 Faraday's time for five years, from 1845 to 1850, and he was now in the 

 sixtieth year of his age. No more great discoveries fell to his lot, but 

 his mind turned more and more to brooding over the consequences of 

 his past discoveries and following out their results. 



The idea of lines of force was still on his mind, and the discovery of 

 diamagnetism had now given him a further insight into their nature. 

 He saw that the magnetic and diamagnetic nature of bodies could be 

 explained by considering them as good or bad conductors of these lines 

 of force. Iron was a good conductor and bismuth a bad one. When 

 soft iron was placed in a magnetic field, the lines of force, or, as we now 

 more exactly term them, the lines of induction, were more easily con- 

 ducted by it than by the air, and they were deflected toward and through 

 it; but a piece of bismuth was a poorer conductor and these lines of 

 force tended to pass around it rather than through it. By surrounding 

 a weak magnetic body by a strong magnetic fluid he found that it pos- 

 sessed all the properties of a diamagnetic one. Pursuing the subject, 

 he showed how the lines of induction were distributed around and within 



