Forces of Electricity, Part II. 335 



other successive portions of air, until it is brought to rest 

 against the charged sphere itself, by which the whole line of 

 inductive action was occasioned. 



70. As it is with visible attraction, so also is it in the case 

 of electrical discharges ; the free electricity is attracted on- 

 ward towards the uninsulated compensator by each of the 

 aerial strata in succession, until at length attaching itself to 

 the former it returns to a state of natural equilibrium. 



71. These principles enable us to understand that neither 

 the discharge of free electricity which we may observe to take 

 place from plus to minus bodies, nor the reciprocal attraction 

 of such bodies by one another, is affected by any direct action 

 they might be supposed to have on one another, but, on the 

 contrary, through the medium of intervening matter; conse- 

 quently it is only in a restricted sense that we may speak 

 of distant bodies compensating or attracting one another. 

 Hence the law of Coulomb must be received only as conven- 

 tional, for although it embraces phgenomena with accuracy, 

 it is palpably fallacious in theory. 



72. We have it in our power, by a very simple method, to 

 verify the conclusion respecting the contiguous action of in- 

 duction, to which we have thus been conducted by the theory. 

 It is in principle as follows : let a plus body be separated from 

 its compensator by an insulating medium of determinate 

 thickness, and the electrical condition induced in the com- 

 pensator be estimated in the ordinary manner by an electro- 

 meter. Then, if induction be independent of the insulating 

 medium, the merging of a second equally plus body, and also 

 of a second similar compensator, in the first respectively 

 should add nothing to the intensity of the induced charge; 

 or to reduce the case to practice, the capacity ofaLeyden jar 

 should increase with the thickness of its metallic coatings, 

 minus some little on account of the minute increase in their 

 mean distances. Now I find, and I believe the fact to be suf- 

 ficiently notorious, that a given electrical charge on one of the 

 coatings of a Leyden pane will exhibit precisely the same in- 

 tensity whether the coatings be composed of films of Dutch 

 metal only, or the very much thicker leaf of tinfoil, even 

 though it be several times repeated. 



73. The view of induction now presented opens up to us 

 the cause of Coulomb's law ; thus advancing us in knowledge 

 another step towards that incomprehensible link which con- 

 nects the immaterial impulse of the Divine Will with the 

 material creation. To understand this cause let us imagine a 

 quantity of free electricity to be accumulated in an insulated 



