878 FRAGMENTS OF SCIENCE 



netism is said to be "induced" in the iron, and hence 

 this mode of magnetizing is called "magnetic induction." 

 Now, there is nothing theoretically perfect in Nature: 

 there is no iron so soft as not to possess a certain 

 amount of coercive force, and no steel so hard as not to 

 be capable, in some degree, of magnetic induction. The 

 quality of steel is in some measure possessed by iron, 

 and the quality of iron is shared in some degree by steel. 

 It is in virtue of this latter fact that the unmagnetized 

 darning-needle was attracted in your first experiment; 

 and from this you may at once deduce the consequence 

 that, after the steel has been magnetized, the repulsive 

 action of a magnet must be always less than its attractive 

 action. For the repulsion is opposed by the inductive 

 action of the magnet on the steel, while the attraction is 

 assisted by the same inductive action. Make this clear 

 to your minds, and verify it by your experiments. In 

 some cases you can actually make the attraction due to 

 the temporary magnetism overbalance the repulsion due 

 to the permanent magnetism, and thus cause two poles of 

 the same kind apparently to attract each other. When, 

 however, good Jiard magnets act on each other from a 

 sufficient distance, the inductive action practically van- 

 ishes, and the repulsion of like poles is sensibly equal 

 to the attraction of unlike ones. 



I dwell thus long on elementary principles, because 

 they are of the first importance, and it is the tempta- 

 tion of this age of unhealthy cramming to neglect them. 

 Now follow me a little further. In examining the distri- 

 bution of magnetism in your strip of steel you raised the 

 needle slowly from bottom to top, and found what we 

 called a neutral point at the centre. Now, does the mag- 



