SPECIFIC INDUCTION, OR SPECIFIC INDUCTIVE CAPACITY. 25 



cording to the method described (11 98. 1207.)) it is evident that the one just receiving 

 its half charge must fall faster in its tension than the other. For suppose app. i. first 

 charged, and app. ii, used to divide with it ; though both may actually lose alike, yet 

 app. i., which has been diminished one half, will be sustained by a certain degree of 

 return action or charge (1234.), whilst app. ii. will sink the more rapidly from the 

 coming on of the particular state. I have endeavoured to avoid this interference 

 by performing the whole process of comparison as quickly as possible, and taking the 

 force of app. ii. immediately after the division, before any sensible diminution of the 

 tension arising from the assumption of the peculiar state could be produced ; and I 

 have assumed that as about three minutes pass between the first charge of app. i. and 

 the division, and three minutes between the division and discharge, when the force of 

 the non-transferable electricity is measured, the contrary tendencies for those periods 

 would keep that apparatus in a moderately steady and uniform condition for the 

 latter portion of time. 



1251. The particular action described occurs in the shell-lac of the stems, as well 

 as in the dielectric used within the apparatus. It therefore constitutes a cause by 

 which the outside of the stems may in some operations become charged with elec- 

 tricity, independent of the action of dust or carrying particles (1203.). 



^ V. On specific induction, or sjpecijic inductive capacity. 



1252. I now proceed to examine the great question of specific inductive capacity, 

 i. e. whether different dielectric bodies actually do possess any influence over the 

 degree of induction which takes place through them. If any such difference should 

 exist, it appeared to me not only of high importance in the further comprehension of 

 the laws and results of induction, but an additional and very powerful argument for 

 the theory I have ventured to put forth, that the whole depends upon a molecular 

 action, in contradistinction to one at sensible distances. 



The question may be stated thus : suppose A an electrified plate of metal suspended 

 in the air, and B and C two exactly similar plates, placed parallel to and on each 

 side of A at equal distances and uninsulated ; A will then induce equally towards B 

 and C. If in this position of the plates some other dielectric than air, as shell-lac, 

 be introduced between A and C, will the induction between them remain the same ? 

 Will the relation of C and B to A be unaltered, notwithstanding the difference of the 

 dielectrics interposed between them ? 



1253. As far as I recollect, it is assumed that no change will occur under such 

 variation of circumstances, and that the relations of B and C to A depend entirely 

 upon their distance. I only remember one experimental illustration of the question, 

 and that is by Coulomb*, in which he shows that a wire surrounded by shell-lac took 

 exactly the same quantity of electricity from a charged body as the same wire in air. 

 The experiment offered to me no proof of the truth of the supposition, for it is not 



* M^moires de TAcademie, 1787, pp. 452, 453. 

 MDCCCXXXVIII. E 



