SUMMARY: NATURE OF INDUCTIVE ACTION. 37 



1294. The insulation was good in all the experiments recorded, except Nos. 10, 15, 

 21, and 25, being those in which ammonia was compared with other gases. When 

 shell-lac is put into ammoniacal gas its surface gradually acquires conducting power, 

 and in this way the lac part of the stem within was so altered, that the ammonia ap- 

 paratus could not retain a charge with sufficient steadiness to allow of division. In 

 these experiments, therefore, the other apparatus was charged ; its charge measured 

 and divided with the ammonia apparatus by a quick contact, and what remained un- 

 taken away by the division again measured (1281 .). It was so nearly one half of the 

 original charge, as to authorize, with this reservation, the insertion of ammoniacal 

 gas amongst the other gases, as having equal power with them. 



1295. Thus induction appears to be essentially an action of contiguous particles, 

 through the intermediation of which the electric force, originating or appearing at a 

 certain place, is propagated to or sustained at a distance, appearing there as a force 

 of the same kind exactly equal in amount, but opposite in its direction and tenden- 

 cies (1164.). Induction requires no sensible thickness in the conductors which may 

 be used to limit its extent ; an uninsulated leaf of gold may be made very highly po- 

 sitive on one surface, and as highly negative on the other, without the least inter- 

 ference of the two states whilst the inductions continue. Nor is it affiscted by the 

 nature of the limiting conductors, provided time be allowed, in the case of those 

 which conduct slowly, for them to assume their final state (1170.). 



1296. But with regard to the dielectrics or insulating media, matters are very dif- 

 ferent (1167.). Their thickness has an immediate and important influence on the 

 degree of induction. As to their quality, though all gases and vapours are alike, 

 whatever their state, amongst solid bodies, and between them and gases, there are 

 differences which prove the existence of specific inductive capacities, these differences 

 being in some cases very great. 



1297. The direct inductive force, which may be conceived to be exerted in lines 

 between the two limiting and charged conducting surfaces, is accompanied by a la- 

 teral or transverse force equivalent to a dilatation or repulsion of these representative 

 lines (1224.) ; or the attractive force which exists amongst the particles of the dielec- 

 tric in the direction of the induction is accompanied by a repulsive or a diverging 

 force in the transverse direction (1304.). 



1298. Induction appears to consist in a certain polarized state of the particles, into 

 which they are thrown by the electrified body sustaining the action, the particles as- 

 suming positive and negative points or parts, which are symmetrically arranged with 

 respect to each other and the inducting surfaces or particles*. The state must be a 



* The theory of induction which I am stating does not pretend to decide whether electricity be a fluid or 

 fluids, or a mere power or condition of recognised matter. That is a question which I may be induced to con- 

 sider in the next or following series of these researches. 



