Cbcorg anD Nature of dfcaanetism. 31 



tempered in just the right way, it will hold its 

 charge if it is given something to do. If a 

 piece of iron is placed across its poles it also 

 becomes a magnet and its molecules turn and 

 work in harmony with those of the mother 

 magnet. These magnetic lines of force reach 

 around in a circuit. Even before the iron, or 

 " keeper," as it is called, is put across its 

 poles there are lines of force reaching around 

 through the air or ether from one pole to an- 

 othrr. (For a description of Ether see Chap. 

 V.) This is called the " field " of the magnet, 

 and when the iron is placed in this field the 

 lines of force pass through it in a closed cir- 

 cuit, and if the "keeper" is large enough to 

 take care of all the lines of force in the field 

 the magnet will not attract other bodies, be- 

 cause its attraction is satisfied, like its proto- 

 type in the molecular ring described above. 



\\'c speak of lines of force, not that force ia 

 necessarily exerted in a bundle of lines but as 

 a convenient way of telling the strength of a 

 magnetic field. The practical limit of the 

 magnetization of soft iron (called saturation) 

 is 18,000 lines to the square centimeter. As 

 long as we give our magnet something to do, 

 up to the measure of its capacity, it will keep 

 up its power. We may make other magnets 

 with it, thousands, yea, millions of them, and 

 it not only does not lose its power but may be 

 even stronger for having done this work. If, 



