4 



of electrical 

 faces with an 



414 Scientific Intelligence. 



charged and neutral plane, was here exhibited to the Section, and was 

 said to be susceptible of great accuracy in measurements of this kind. 

 The author supposes every case of electrical attraction to resolve itself 

 into the conditions of the Leyden experiment, and to be a simple case 



charge obtained by the opposition of two conducting sur- 

 intervening nonconducting medium ; and it is well known 

 that in the electrical jar the charge is not dependent on the thickness 

 of the coatings but on their extension. If we could suppose a single 

 body only in the universe — and to be charged with electricity — there 

 appears no reason from experiment to suppose a priori, an unequal 

 distribution upon it, be the form what it may ; but if we conceive a 

 second body to be called into existence, then the action termed electri- 

 cal induction arises between the two, which is again reflected back by 

 the second body upon the first ; and on a space void of resistance this 

 induction, however small, would cause an electrical current to flow 

 through a space however great; but if a resisting nonconducting medi- 

 um be interposed between these bodies, then we have to consider the 

 action upon the interposed particles, and we have immediately a case 

 of charge between the opposed surfaces of the two bodies, — and which 

 will be greater in proportion to the amount of induction or electrical 

 disturbance of which the previously neutral body is susceptible. In 

 this way we may consider any two conducting bodies when opposed to 

 each other as forming the coatings to an intermediate mass of air, and 

 these are all the conditions we have to consider. In the case of two 

 spheres opposed to each other, one insulated and charged with a given 

 quantity of electricity, the other uninsulated and free, the determina- 

 tion of the laws of the attractive force was simple and the problem 

 easy of solution, without any complicated consideration of an hypo- 

 thetical distribution of the electricity upon the spheres and conductors 

 connected with them ;— we had, in fact, a chargeable system, with 

 convex coatings. We have only to consider the opposed areas. Here, 

 'n whatever way the primary forces between the surfaces may be con- 



ceived to exist, they are finally reduced to an action between oppos 

 and similar points, depending on the engagement of opposed positive 

 and negative forces, by which an exclusive action between certain 

 points is established. The attractive force between the spheres o^ 

 rather opposed hemispheres, is as the number of attracting points, an 

 inversely, and as the squares of the distances inversely ; we can henc^ 

 determine the position of two points q q' within the surface of eac^ 

 opposed hemisphere in which we may conceive the whole force to 

 collected, and to be the same as if derived from every point on 

 surface. The whole force will vary as the squares of the disl ^. 

 between these points inversely ; so that a unit of force at a unit o 

 tance between the nearest points of the spheres being given, [tlse [ J m 

 to assign or predict the force at any other distance at which the in^ 

 mediate air can become charged. The following formula was gi ^ 

 by the author for determining the distance of the points q q f within 



t (a z 4-2ar)i — a _. rt n r the 



hemisphere : *=— ~ J In which % is the distance of 



point q, a the distance between the nearest points of the spheres, 

 r the radius. When both hemispheres are equal, the whole force 



