MAGNETIC ATTRACTION. 



of pulling there is no action at a distance ; 

 the distance is bridged by some material con- 

 nection. 



The child's astonishment, therefore, when 

 first it sees the toy-swan pulled by the magnet 

 without contact is a perfectly philosophic 

 state of mind. It is noting an experience of a 

 new kind. 



Later in life we get more habituated to the 

 idea of pulling at a distance, and often call it 

 suction, as when we say that the pump-bucket 

 sucks or draws water which is many feet below 

 in the cistern. In still higher development 

 we seem to possess means of drawing a boat 

 when by Hertzian waves we steer it towards the 

 shore without having any apparent material 

 connection with it. And a form of pulling at a 

 distance which extends through all the known 

 universe, though its nature and extension were 

 long unrecognised, is the universal gravitation 

 discovered by Newton. 



The most familiar of these instances, that 

 of the pump, is now well known not to be a 

 case of suction at all, as the word is commonly 

 understood. The bucket at A (Fig. 41) has 

 no mysterious power of drawing the water at 

 B, and, in fact, does not draw it, though it is 

 usually spoken of as doing so. 



What the bucket A does is to lift and push 

 up the air at A, which would otherwise press 

 downwards upon the water at B with a force 



187 



