NOMOS. . 57 



current through one coil gives rise to a current in 

 the companion coil. If the conductor be coiled into 

 a tubular helix, as in an experiment we shall have to 

 dwell upon presently, and a bar of iron or steel 

 introduced into the core, the magnetic properties of 

 the helix, when a current is passed through it, are 

 found to be reproduced in the bar by the induction 

 of corresponding currents around it. The magnetic 

 needle, moreover, detects the presence of currents in 

 the neighbourhood of a conductor similar to those 

 which are passing through the conductor at the time. 

 Hence it is a fair inference that the current which 

 passes through the wire is not confined to the wire, 

 but that it overflows to a greater or less distance 

 from the wire. When two wires are placed parallel 

 to each other, and a current is passed through each 

 in the same direction, the results then are similar. 

 In neither case is the current confined to its proper 

 wire ; and in reality each current must be supposed 

 to pass through the other wire and its immediate 

 neighbourhood as well as through its own wire and 

 the immediate neighbourhood ; and thus, mutually 

 overflowing, the result must be that each current will 

 co-operate with and intensify the other. This must 

 be the result, for it is an ascertained fact that cur- 

 rents will intensify each other when passing in the 

 same direction, and neutralise each other when passing 

 in contrary directions. And if all this be so, it fol- 

 lows from the premises that the wires will attract 

 each other when the currents pass in the same 

 direction. What are these currents? They are 

 composed of molecules, which molecules have common 



