488 Royal Socict?/:— 



down or reverse the polarized state of the dialcctric medium impeding 

 discharge, as between the exploding halls of the Lane's discharger : 

 this is as the quantity of charge directly. In employing these terms, 

 the author has not the least view to any specific changes in the quality 

 or condition of the accumulated electricity, as relating to density, 

 elasticity, and such like. Whether the tension and intensity of a 

 charge, as evidenced by the electrometer, be great or little, he con- 

 ceives that the nature of the force and its mode of operation remains 

 the same. Viewing the process of electrical accumulation and dis- 

 charge in the Leyden jar as the result of certain powers or forces 

 operating either immediately through the glass or through an external 

 circuit, or both, we may readily imagine that at the critical point at 

 which the forces in the two directions become balanced, and at which 

 point the equilibrium of charge is, at it were, overset on the side of 

 the exterior circuit, then it is that residual charge ensues, either by a 

 momentary revulsion of force between the coatings in the direction of 

 the intervening glass, frequently causing fracture, or otherwise by a 

 retention of some of the charge in that direction at the instant of 

 explosion. Some instructive and important experiments by Mr. T. 

 Howldy are here quoted in support of this conclusion, from the 

 pages of the ' Philosophical Magazine ' for the year 1815. A ruptured 

 jar had the coatings removed from around the perforated part, so as to 

 admit of the jar receiving a given amount of charge. When explosive 

 discharge took place in the usual way, a spark was observed to pass at 

 the same instant between the coatings through the perforation in the 

 glass, evidently showing an exertion of force in that direction. This 

 spark is entirely independent of the discharge in the circuit, the 

 force of which remains the same as if no such perforation existed, as 

 Priestley and other electricians, and Mr. Howldy himself, have fully 

 demonstrated. 



Considering the question of residual charge as bearing materially on 

 our views of the nature of electrical force, the author seeks to inves- 

 tigate, by new forms and kinds of experiment, the relation of the 

 residual quantity to the whole charge, whether accumulated on glass 

 coated with very perfect conductors such as the metals, or otherwise 

 with less perfect conductors, as water, or with imperfect conductors, 

 such as paper, linen and the like. The instruments employed are 

 now enumerated and commented on, and their experimental arrange- 

 ment figured and described. They consist of the electrical or Leyden 

 jar; Lane's improved electrometer; the hydrostatic electrometer 

 as recently perfected ; the thermo-electrometer ; quantity or unit- 

 measure ; and battery charger and discharger. The following is the 

 course which the author pursued in his inquiries, through the medium 

 of these instruments. 



The quantity of charge being given, its intensity is measured by 

 the hydrostatic electrometer in terms of attractive force at a constant 

 distance, suppose at distance 1 inch. This is first noted : the jar is 

 now discharged through its exploding distance by completing the 

 circuit through the Lane's discharger. The hydrostatic electro- 

 meter, being now made perfectly neutral, is again brought into con- 



