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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- 

 nexion with the inner coating of the jar. The intensity or attractive 

 force of the residuary or remaining charge is now noted, but as this 

 force is necessarily small, it is taken with the attracting plates at a 

 diminished distance from '1 to *3 of an inch or more, as the case may 

 require, and subsequently reduced to the standard distance of one 

 inch, taking the force to vary, as demonstrable by the electrometer, 



as pr 2 . This being determined, the relative quantities of electricity 

 in the full charge and the residual charge will be as the square roots 



