CONTRIBUTIONS TO SCIENCE. 537 



Again, suppose two parallel wires to be near together 

 and to convey currents in opposite directions. The strength 

 of a current determines the difference between the velo- 

 cities of the molecular vortices on opposite sides of it, 

 the electric [particles being related to the vortices in the 

 same way as a differential wheel in mechanism ; but the 

 vortices on one side of a moving stream of electric particles 

 may be brought to rest if the velocity of those on the other 

 side be doubled, the current remaining the same though the 

 electric particles themselves will now have to spin round, 

 but this makes no difference. Hence, when parallel wires 

 convey currents in opposite directions, the vortices between 

 them being made to spin in the same direction by both 

 currents, will rotate faster than those on the opposite sides 

 of the wires, and pressing as they do with force proportional 

 to the squares of their circumferential velocities, the wires 

 will be pushed apart as if they repelled one another. 



When two parallel wires convey currents in the same 

 direction, they tend to make the cells in the space between 

 them spin in opposite directions, and the velocities of the 

 molecular vortices there will consequently be less than on 

 the other side of the wires. The pressure of the medium 

 between the wires will therefore be less than in the space 

 beyond, and the wires will be pushed together as if they 

 attracted one another. 



Now, suppose that a current of electricity commences 

 to flow in a wire. Molecular vortices will be set up in the 

 immediate neighbourhood of the wire, and these vortices 

 acting on the electric particles on the other side of them, 

 remote from the wire, will endeavour to set them in motion 

 in the direction opposite to the current in the wire. But if 

 the medium be a dielectric, the particles cannot be displaced 

 through a sensible distance. They will therefore be made to 

 rotate and start another and larger layer of vortices surround- 

 ing the wire, and so the motion will be propagated as above 

 explained. But suppose that at a certain distance there is 

 placed another wire parallel to the first, and forming part 

 of a closed circuit in which no current is flowing. The 



