488 Mr. Laming oji the primary Forces of Electricity, 



so small that its attractive force in no case exceeded the j^-th 

 part of a grain, the accordance of these results with Coulomb's 

 law is more perfect than could have been expected. The 

 necessity for so minute a charge had previously been ascer- 

 tained by finding, on the approach of the attracting surfaces 

 being mechanically prevented, that a quantity of electricity 

 the attractive force of which was under a grain, passed to the 

 negative body in a diffused discharge. 



3. We may now notice a corollary to this law of electrical 

 attraction which seems hitherto to have escaped notice ; 

 namely, the definite nature of the electrical attraction. It will 

 be at once evident, that if a given quantity of electricity ex- 

 erted an attractive force on common matter without reference 

 to quantity, an electrical action set up between any two 

 given bodies would, by Coulomb's law, continue constant so 

 long as their distance from one another remained unaltered, 

 whatever changes might be taking place in the relative situa- 

 tions of contiguous bodies. That this is not the case, we are 

 assured by the commonest observation ; for nothing is better 

 known than the interception of the electrical force between 

 two dissimilarly charged bodies by the intervention or near 

 approach of a third. 



4. By this we see that the attraction which is reciprocal 

 between electricity and common matter, must be definite with 

 regard to quantity as well as force ; and as we examine the 

 following pages we shall find such abundant and conclusive 

 evidences of the same fact as will make it irresistible. The 

 cause for the opposite opinion having been so long adhered 

 to is the susceptibility of common matter to undergo an aug- 

 mentation or diminution of its natural quantity, — a term, by 

 the by, of itself sufficiently expressive of a certain undefined 

 but commonly prevailing notion of saturation : this subject 

 will shortly come more fully under consideration, when we 

 shall take occasion to show that these changes in quantity are 

 not only quite compatible with the alleged definite attrac- 

 tions, but a necessary consequence of a second, and, I believe, 

 hitherto unsuspected electrical force, the entity of which it will 

 then devolve upon me to establish. 



5. Since then common matter is naturally associated with 

 a definite quantity of electricity, we are required by strict phi- 

 losophical reasoning to believe that each atom of that matter 

 contributes its part to the general effect by attracting to itself 

 its own equivalent of electricity ; and for this doctrine we have 

 been in a measure prepared by the admirable experimental 

 researches of Dr. Faraday on the definite nature of galvanic 

 analysis. 



