1220.  To suppose that the upper part of the uninsulated ball B, should in some way be retained in an electrified state by that portion of the surface of the ball which is in sight of the shell-lac, would be in opposition to what we know already of the subject.  Electricity is retained upon the surface of conductors only by induction (1178.); and though some persons may not be prepared as yet to admit this with respect to insulated conductors, all will as regards uninsulated conductors like the ball B; and to decide the matter we have only to place the carrier ball at e (fig. 107.), so that it shall not come in contact with B, uninsulate it by a metallic rod descending perpendicularly, insulate it, remove it, and examine its state; it will be found charged with the same kind of electricity as, and even to a higher degree (1224.) than, if it had been in contact with the summit of B.

1221.  To suppose, again, that induction acts in some way through or across the metal of the ball, is negatived by the simplest considerations; but a fact in proof will be better.  If instead of the ball B a small disc of metal be used, the carrier may be charged at, or above the middle of its upper surface:  but if the plate be enlarged to about 1-1/2 or 2 inches in diameter, C (fig. 108.), then no charge will be given to the carrier at f, though when applied nearer to the edge at g, or even above the middle at h, a charge will be obtained; and this is true though the plate may be a mere thin film of gold-leaf.  Hence it is clear that the induction is not through the metal, but through the surrounding air or dielectric, and that in curved lines.

1222.  I had another arrangement, in which a wire passing downwards through the middle of the shell-lac cylinder to the earth, was connected with the ball B (fig. 109.) so as to keep it in a constantly uninsulated state.  This was a very convenient form of apparatus, and the results with it were the same as those just described.

1223.  In another case the ball B was supported by a shell-lac stem, independently of the excited cylinder of shell-lac, and at half an inch distance from it; but the effects were the same.  Then the brass ball of a charged Leyden jar was used in place of the excited shell-lac to produce induction; but this caused no alteration of the phenomena.  Both positive and negative inducing charges were tried with the same general results.  Finally, the arrangement was inverted in the air for the purpose of removing every possible objection to the conclusions, but they came out exactly the same.