398 RECENT PROGRESS IN PHYSICS. 



Faraday's theory does not pretend to decide upon the consequences 

 of a vacuum. According to his view, electrical phenomena, such as 

 induction, conduction^ and insulation, depend on, and are produced 

 hy, the influence of contiguous particles of matter, the nearest particle 

 being considered as the contiguous one ; he assumes further, that these 

 particles become polarized, and that they act at a distance only by 

 acting on the contiguous and intermediate particles. 



Suppose a vacuum to be in the line of induction ; it does not follow 

 from the theory, says Faraday, that the particles on the opposite sides 

 of such a vacuum cannot act on each other. Suppose it possible for a 

 positively electrified particle to exist in the centre of a vacuum one 

 inch in diameter ; nothing in my theory prevents the particle from 

 acting, at the distance of half an inch, on all the particles forming 

 the surface of the sphere with a force according to the known law of 

 the square of the distance. 



Here, however, Faraday again assumes the action at a distance. 



In the fourteenth series of Experimental Researches, (Fog. Ann. 

 Sup., vol. of 1842,) i^arac?a?/ collected his views on the nature of elec- 

 trical force, and particularly on the state of tension accompanying 

 induction. I quote this summary literally : 



'^ 1669. The theory {Faraday' s) assumes that all the particles, 

 whether of insulating or conducting matter^ are, as wholes, con- 

 ductors. 



" 1670. That not being polar in their normal state, they can become 

 so by the influence of neighboring charged particles, the polar state 

 being developed at the instant, exactly as in an insulated conducting 

 mass consisting of many particles. 



" 1671. That the particles when polarized are in a forced state, and 

 tend to return to their normal or natural condition. 



" 1672. That being as wholes conductors, they can readily be 

 charged, either bodily or 2^olarly. 



" 1673. That particles which, being contiguous, are also in the line 

 of inductive action, can communicate or transfer their polar forces one 

 to another more or less readily. 



" 1674. That those doing so less readily require the polar force to 

 be raised to a higher degree before this transference or communication 

 takes place. 



" 1675. That the ready communication of forces between contiguous 

 particles constitutes conduction, and the difficult communication insu- 

 lation; conductors and insulators being bodies whose particles natur- 

 ally possess the property of communicating their respective forces 

 easily or witli difficulty ; having these differences just as they have 

 differences of any other natural property. 



"1676. That ordinary induction is the effect resulting from, the 

 action of matter charged with excited or free electricity upon insu- 

 lating matter, tending to produce in it an equal amount of the contrary 

 state. 



"1677. That it [the charged matter] can do this only by polarizing 

 the particles continguous to it, which perform the same office to the 

 next and these again to those beyond ; and that thus the action is 

 propagated from the excited body to the next conducting mass, and 

 these render the contrary force evident in consequence of the effect ot 



