CH. xxxvi. ELECTRO-MAGNETS. 373 



a current through it (see Fig. 66). After a short time he 

 took the bar out and found it was a perfect bar magnet, 

 which would attract iron. The current of electricity, in 

 circulating round the steel, had magnetised the steel just as 

 if it had been rubbed on a loadstone. 



With steel the magnetism remained after it was taken out 

 of the electric coil, but if he used a piece of ordinary soft 

 iron the magnetism passed away when the current ceased. 

 He called these magnetised bars electro-magnets, because 

 they are made by electricity. You can easily make them 

 for yourself if you have a small electric battery, and you 

 will find that an iron rod will hold up needles, nails, or even 

 keys as long as the current is passing, but they will all fall 



^^ 



FIG. 66. 

 Coil of Copper Wire conveying an Electric Current round a Steel Bar. 



off soon after it stops, showing that it is the electric current 

 which causes the iron to act as a magnet. 



Professor Arago, whom we mentioned before (p. 324) as 

 making experiments on light, succeeded in magnetising a 

 steel bar with currents from an ordinary electrical machine, 

 that is, a glass cylinder rubbed against silk, instead of using 

 a battery. 



Michael Faraday, 1791-1867. We must now travel 

 back to England, where one of our greatest philosophers was 

 watching these new discoveries with intense interest. Michael 

 Faraday, the son of a poor journeyman blacksmith, was born 

 at Newington Butts in 1791. When he was thirteen years 

 old he went as errand boy to a bookseller named Riebau 

 in Blandford Street, Manchester Square, and it was there that 

 the books fell into his hands which first awoke his love 

 of science. Mrs. Marcet's ' Conversations on Chemistry,' 



