[From the . Proceedings of the Royal Institution of Great Britain, Vol. vn.] 



LIV. On Action at a Distance. 



I HAVE no new discovery to bring before you this evening. I must ask 

 you to go over very old ground, and to turn your attention to a question 

 which has been raised again and again ever since men began to think. 



The question is that of the transmission of force. We see that two bodies 

 at a distance from each other exert a mutual influence on each other's motion. 

 Does this mutual action depend on the existence of some third thing, some 

 medium of communication, occupying the space between the bodies, or do the 

 bodies act on each other immediately, without the intervention of anything else ? 



The mode in which Faraday was accustomed to look at phenomena of this 

 kind diners from that adopted by many other modern inquirers, and my special 

 aim will be to enable you to place yourselves at Faraday's point of view, and to 

 point out the scientific value of that conception of lines of force which, in his 

 hands, became the key to the science of electricity. 



When we observe one body acting on another at a distance, before we 

 assume that this action is direct and immediate, we generally inquire whether 

 there is any material connection between the two bodies ; and if we find strings, 

 or rods, or mechanism of any kind, capable of accounting for the observed 

 action between the bodies, we prefer to explain the action by means of these 

 intermediate connections, rather than to admit the notion of direct action at a 

 distance. 



Thus, wheii we ring a bell by means of a wire, the successive parts of 

 the wire are first tightened and then moved, till at last the bell is rung at 

 a distance by a process in which all the intermediate particles of the wire have 

 taken part one after the other. We may ring a bell at a distance in other 

 ways, as by forcing air into a long tube, at the other end of which is a 

 cylinder with a piston which is made to fly out and strike the bell. We 



