GENERAL NATURE OF INDUCTIVE ACTION. 267 



lation to all those contiguous to it, just as one magnet can affect two or more mag- 

 netic needles near it, and these again a still greater number beyond them. Hence 

 would result the production of curved lines of inductive force if the inducteous body- 

 in such a mixed dielectric were an uninsulated metallic ball (1219. &c.) or other pro- 

 perly shaped mass. Such curved lines are the consequences of the two electric forces 

 arranged as I have assumed them to be : and, that the inductive force can be directed 

 in such curved lines is the strongest proof of the presence of the two powers and the 

 polar condition of the dielectric particles. 



1680. I think it is evident that in the case stated, action at a distance can only re- 

 sult through an action of the contiguous conducting particles. There is no reason 

 why the inductric body should polarize or affect distant conductors and leave those 

 near it, namely the particles of the dielectric, unaffected : and everything in the form 

 of fact and experiment with conducting masses or particles of a sensible size con- 

 tradicts such a supposition. 



1681 . A striking character of the electric power is that it is limited and exclusive, and 

 that the two forces being always present are exactly equal in amount. The forces are 

 related in one of two ways, either as in the natural normal condition of an uncharged 

 insulated conductor ; or as in the charged state, the latter being a case of induction. 



1682. Cases of induction are easily arranged so that the two forces being limited 

 in their direction shall present no phenomena or indications external to the apparatus 

 employed. Thus if a Leyden jar, having its external coating a little higher than the 

 internal, be charged and then its charging ball and rod removed, such jar will present 

 no electrical appearances so long as its outside is uninsulated. The two forces which 

 may be said to be in the coatings, or in the particles of the dielectric contiguous to 

 them, are entirely engaged to each other by induction through the glass ; and a 

 carrier ball (1181.) applied either to the inside or outside of the jar will show no signs 

 of electricity. But if the jar be insulated, and the charging ball and rod, in an un- 

 charged state and suspended by an insulating thread of white silk, be restored to 

 their place, then the part projecting above the jar will give electrical indications and 

 charge the carrier, and at the same time the outside coating of the jar will be found 

 in the opposite state and inductric towards external surrounding objects. 



1683. These are simple consequences of the theory. Whilst the charge of the 

 inner coating could induce only through the glass towards the outer coating, and the 

 latter contained no more of the contrary force than was equivalent to it, no induction 

 external to the jar could be perceived; but when the inner coating was extended by 

 the rod and ball so that it could induce through the air towards external objects, 

 then the tension of the polarized glass molecules would, by their tendency to return 

 to the normal state, fall a little, and a portion of the charge passing to the surface of 

 this new part of the inner conductor, would produce inductive action through the air 

 towards distant objects, whilst at the same time a part of the force in the outer coat- 

 ing previously directed inwards would now be at liberty, and indeed be constrained to 



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