110 Answer to Dr. Harems Letter. 



each other. A and C will not be in this polarized state, for they 

 will each be as it is said charged (ill) ; the one positively, the other 

 negatively ; and they will present no polarity as far as this partic- 

 ular act of induction (iv) is concerned, 



vi. That one part of A is more positive than another part does 

 not render it polar in the sense in which that word has just been 

 used. We are considering a particular case of induction and have 

 to throw out of view the states of those parts not under the in- 

 ductive action. Or if any embarrassment still arise from the fact 

 that A is not uniformly charged all over, then we have merely to 

 surround it with balls such as B and C on every side so that its 

 state shall be alike on every part of its surface, (because of the 

 uniformity of its inductive influence in all directions,) and then 

 that difficulty will be removed. A, therefore is charged but not 

 polarly, B assumes a polar condition, and C is charged inducteously 

 (1483); being, by the prime influence of A brought into the op- 

 posite or negatively electrical state through the intervention of the 

 intermediate and polarized ball B. 



vii. Simple charge therefore does not imply polarity in the body 

 charged. Inductive charge (applying that term to the sphere B 

 and all bodies in a similar condition (v) ) does (1672,) The 

 word charge, as applied to a Leyden jar or to the whole of any 

 inductive arrangement, by including all the effects, comprehends 

 of course both these states. 



viii. As another expression of my theory, I will put the follow- 

 ing case. Suppose a metallic sphere C formed of a thin shell a 

 foot in diameter ; suppose also in the centre of it another metallic 

 sphere A, only an inch in diameter ; suppose the central sphere 

 A charged positively with electricity to the amount we will say 

 of 100 : it would act by induction through the air, lac, or other 

 insulator between it and the large sphere C ; the interior of the 

 latter would be negative, and the exterior positive, and the sum 

 of the positive force upon the whole of the external sphere would 

 be 100. The sphere C would in fact be polarized (v) as regards 

 its inner and outer surfaces. 



ix. Let us now conceive that instead of mere air or other insu- 

 lating dielectric within C, between it and A, there is a thin metal- 

 he concentric sphere, six inches in diameter. This will make no 

 difference in the ultimate result ; for the charged ball A will ren- 

 der the inner and outer surfaces of the sphere B negative and 



