38 



of many dissimilar phsenomena to one single comprehensive law. 

 As the whole effect upon the electrolyte appeared to be an action 

 of the particles when thrown into a peculiar polarized state, he was 

 led to suspect that common induction itself is in all cases an action 

 of contiguous particles, and that electrical action at a distance, which 

 is what is meant by the term induction, never occurs except through 

 the intermediate agency of intervening matter. He considered that a 

 test of the correctness of his views might be obtained by tracing the 

 course of inductive action ; for if it were found to be exerted in curved 

 lines it would naturally indicate the action of contiguous particles, 

 and would scarcely be compatible with action at a distance. More- 

 over, if induction be an action of contiguous particles, and likewise 

 the first step in electrolyzation, there seemed reason to expect some 

 particular relation of this action to the different kinds of matter 

 through which it is exerted ; that is, something equivalent to a 

 specific electric induction for different bodies ; and the existence of 

 such specific powers would be an irrefragable proof of the dependence 

 of induction on the intervening particles. The failure of all attempts 

 to produce an absolute charge of electricity of one species alone, in- 

 dependent of the other, first suggested to the author the notion 

 that induction is the result of actions among the individual and con- 

 tiguous particles of matter, having both forces developed to an ex- 

 tent exactly equal in each particle. 



The author describes various experiments, with the view of show- 

 ing that no case ever occurs in which an absolute charge of one spe- 

 cies of electricity can be given. His first experiments were conducted 

 on a very large scale : an insulated cube, twelve feet in the side, 

 consisting of a wooden frame, with wire net- work, every part of 

 which was brought into good metallic contact by bands of tin foil, 

 had a glass tube, containing a wire in connexion with a large elec- 

 trical machine, passed through its side, so that about four feet of the 

 tube entered within the cube and two feet remained without ; but it 

 was ^ound impossible in any way to charge the air within this appa- 

 ratus with the least portion of either electricity. 



For investigating the question whether induction is an action of 

 contiguous particles, the author employed, as an electrometer, the 

 torsion balance of Coulomb with certain alterations and additions ; 

 and for deciding that of specific inductive capacity, a new apparatus, 

 constructed for that express purpose. This apparatus consisted of 

 two hollow brass spheres, of very unequal diameters, the smaller 

 placed within the larger, and concentric with it ; the interval be- 

 tween the two being the space through which the induction was to 

 be effected. The apparatus had a tube in the lower part, furnished 

 with a stop-cock, by means of which it might be connected with an 

 air-pump or filled with any required gas. In place of the lower hemi- 

 spherical shell of air, occupying the interval between the two 

 spheres, any solid dielectric, of the same form, such as shell-lac, 

 glass, or sulphur, might be substituted. Two of these instruments, 

 precisely similar in every respect, were constructed, and the author 

 ascertained that the inductive power was the same in both, by alter- 



