ON PHYSICAL LINES OF FORCE. 



(4) The vortices are separated from each other by a single layer of round 

 particles, so that a system of cells is formed, the partitions being these layers 

 of particles, and the substance of each cell being capable of rotating as a vortex. 



(5) The particles forming the layer are in rolling contact with both the 

 vortices which they separate, but do not rub against each other. They are 

 perfectly free to roll between the vortices and so to change their place, provided 

 they keep within one complete molecule of the substance ; but in passing from 

 one molecule to another they experience resistance, and generate irregular 

 motions, which constitute heat. These particles, in our theory, play the part of 

 electricity. Their motion of translation constitutes an electric current, their 

 rotation serves to transmit the motion of the vortices from one part of the 

 field to another, and the tangential pressures thus called into play constitute 

 electromotive force. The conception of a particle having its motion connected 

 with that of a vortex by perfect rolling contact may appear somewhat awkward. 

 I do not bring it forward as a mode of connexion existing in nature, or even 

 as that which I would willingly assent to as an electrical hypothesis. It is, 

 however, a mode of connexion which is mechanically conceivable, and easily 

 investigated, and it serves to bring out the actual mechanical connexions 

 between the known electro-magnetic phenomena ; so that I venture to say that 

 any one who understands the provisional and temporary character of this 

 hypothesis, will find himself rather helped than hindered by it in his search 

 after the true interpretation of the phenomena. 



The action between the vortices and the layers of particles is in part 

 tangential ; so that if there were any slipping or differential motion between 

 the parts in contact, there would be a loss of the energy belonging to the 

 lines of force, and a gradual transformation of that energy into heat. Now we 

 know that the lines of force about a magnet are maintained for an indefinite 

 time without any expenditure of energy ; so that we must conclude that 

 wherever there is tangential action between different parts of the medium, there 

 is no motion of slipping between those parts. We must therefore conceive that 

 the vortices and particles roll together without slipping ; and that the interior 

 strata of each vortex receive their proper velocities from the exterior stratum 

 without slipping, that is, the angular velocity must be the same throughout each 

 vortex. 



within it, and that the existence of this rotation might be detected by experiments on the free rotation of a 

 magnet. I have made experiments to investigate this question, but have not yet fully tried the apparatus. 



