AKD MODEM PHYSICS. 173 



Maxwell states that 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," ho writes, " as a mode of 

 connection existing in Nature, or even as that which 

 I would willingly assent to as an electrical hypothesis. 

 It is, however, a mode of connection which is mechani- 

 cally conceivable and easily investigated, and it serves 

 to bring out tho actual mechanical connections 

 between tho known electro-magnetic phenomena, so 

 that I venture to say that anyone who understands 

 tho provisional and temporary character of this 

 hypothesis will find himself rather helped than 

 hindered by it in his search after the true interpreta- 

 tion of the phenomena." 



The first part of the paper deals with the theory 

 of magnetism ; in tho second part the hypothesis is 

 applied to tho phenomena of electric currents, and it 

 is shown how tho known laws of steady currents and 

 of electro-magnetic induction can bo deduced from it. 

 In Part III., published January and February, 1802, tho 

 theory of molecular vortices is applied to statical 

 electricity. 



Tho distinction between a conductor and an 

 insulator or dielectric is supposed to be that in the 

 former the particles of electricity can pass with more 

 or less freedom from molecule to molecule. In the 

 latter such transference is impossible, the particles can 

 only bo displaced within the molecule with which 

 they ore connected; tho cells or vortices of the 

 medium are supposed to bo elastic, and to resist by 

 their elasticity the displacement of the particles within 



