THE PATH OF EVOLUTION 



in proper contact therewith. If the iron is soft that 

 is, pure the magnetism will continue in it only so 

 long as they are in electric contact ; but if the iron 

 is hard that is, if it, like hardened steel, contains a 

 small amount of chemically combined Carbon, and the 

 contact be maintained for some time the steel-like 

 iron, will acquire permanent magnetism equal to the 

 original magnet, though the latter will lose none of 

 its own. 



If an electric current from any source is caused to 

 pass through an insulating-covered wire (a conductor), 

 making many spiral coils around a rod or other mass 

 of iron, the iron, if soft and pure, will become a 

 strong magnet, but will lose its magnetism instantly on 

 interruption of the electric flow. On this property de- 

 pends to a great extent the application of electricity to 

 the dynamo, the telegraph and most of its other uses. 

 If steel or hard iron is used in place of soft iron, it 

 will acquire permanent magnetism. It is thus that 

 magnets now are practically made. How or why the 

 Black oxide of iron and why hard iron should pos- 

 sess this strange power of retaining magnetism per- 

 manently, themselves undergoing no chemical or 

 physical change, is inexplicable. Within the last 

 twenty years the application of Electricity and of 

 electro-magnetism to new and important uses have 

 been so numerous as nearly to revolutionize the pro- 



186 



