The object of this paper is to establish two general principles re­lating to the theory of electricity, which appear to be of great im­portance; first, that induction is in all cases the result of the actions of contiguous particles; and secondly, that different insulators have different inductive capacities. The class of phænomena usually arranged under the head of induction are reducible to a general fact, the existence of which we may recognise in all electrical phænomena whatsoever; and they involve the operation of a principle having all the characters of a first, essen­tial and fundamental law. The discovery which he had already made of the law by which electrolytes refuse to yield their elements to a current when in the solid state, though they give them forth freely when liquid, suggested to the author the extension of analogous ex­planations with regard to inductive action, and the possible reduction of many dissimilar phænomena 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 con­tiguous particles of matter, having both forces developed to an ex­tent exactly equal in each particle.