39 



nately charging each and dividing the charge with the other, and 

 finding that, in all cases, the charge remaining in the one, and also 

 that received by the other, was very nearly half the original charge. 



The experiments on which the author principally relies in support 

 of the correctness of his views relative to induction being exerted in 

 curved lines, are the following : a brass ball being laid on the top 

 of an excited cylinder of shell-lac placed vertically, the charge 

 which a carrier ball received when brought to diiFerent points near 

 to the brass sphere was measured by means of the electrometer ; and it 

 was inferred, from the character of the electricity, that the charge 

 was one by induction, and from its measure, that it proceeded in 

 curved lines. By substituting for the brass sphere a disc of metal 

 above the shell-lac cylinder, it was found that when the carrier ball was 

 brought near to the middle of the disc no charge was communicated, 

 although a sensible one was obtained at the edge of the disc, and 

 also at a point above its centre, farther removed from the excited 

 cylinder. Corresponding and very striking results were obtained 

 when a brass hemisphere was placed on the top of the cylinder of lac. 

 The charge communicated at the centre of the hemisphere was only 

 one-third of that obtained at the edge of its periphery ; but by taking 

 it at a point at some height above the centre, and consequently much 

 farther removed from the inducing cause, the charge was nearly 

 equal to that of the periphery. Here, the author remarks, the in- 

 duction fairly turned a corner, exhibiting both the curved lines or 

 courses of its action, when disturbed from their rectilineal form by 

 the shape, position and condition of the metallic hemisphere ; and 

 also a lateral tension, so to speak, of these lines on one another ; all 

 depending on induction being an action of the contiguous particles 

 of the dielectric thrown into a state of polarity and tension, and mu- 

 tually related by their forces in all directions. In the foregoing ex- 

 periments the (Helectric was air; but they were afterwards varied by 

 substituting a fluid, as oU of turpentine, and likewise a few solid 

 dielectrics, namely, shell-lac, sulphur, carbonate and borate of lead, 

 flint-glass, and spermaceti, and with these, corresponding results 

 were obtained. These results, the author considers, cannot but be 

 admitted as arguments against the received theory of induction, 

 and in favour of that which he has put forth. 



In the course of these experimental researches, some effects due 

 to conduction, which had not been anticipated, and which were si- 

 milar to the residual charge in the Ley den jar, had been obtained 

 with such bodies as glass, lac, sulphur, &c. If the inductive appa- 

 ratus, fitted with a hemispherical cup of shell-lac, after having re- 

 mained charged for fifteen or twenty minutes, was suddenly and per- 

 fectly discharged, and then left to itself, it would gradually recover 

 a very sensible charge ; the electricity which thus returned from an 

 apparently latent to a sensible state being always of the same kind 

 as that given by the charge. This return charge is attributed to an 

 actual penetration, by conduction, of the charge to some distance 

 within the dielectric at each of its two surfaces, and several experi- 



