•l~i'l PHILOSOPHICAL TRANSACTIONS. [ANNO 1782. 



some time; in which case the intensity being reduced almost to nothing, the 

 electricity will pass to the inferior plane exceeding slowly. 



But the case will not be the same if, in performing this experiment, the elec- 

 trified metal plate be made to touch the inferior plane edgewise ; for then its in- 

 tensity being greater than when laid flat, as appears by the electrometer, the 

 electricity easily overcomes the small resistance, and passes to the inferior plane, 

 even across a thin stratum ;* because the electricity of the one plane is balanced 

 by that of the other, only in proportion to the quantity of surface which they 

 oppose to each other within a given distance ; and when the metal plate touches 

 the other plane in flat and ample contact its electricity is not dissipated. This 

 apparent paradox is clearly explained by the theory of electric atmospheres. 



Hitherto we have considered in what manner the action of electric atmos- 

 pheres must modify the electricity of the metal plate in its various situations. 

 We must now consider the effects which take place when the electricity is com- 

 municated to the metal plate while standing on the proper plane. The whole 

 business having been proved in the preceding pages, it is easy to deduce the ap- 

 lications from it ; yet it will be useful to exemplify it by an experiment. Sup- 

 pose that a Leyden phial, or a conductor, were so weakly electrified that the in- 

 tensity of its electricity was only of half a degree or even less : if the metal 

 plate of our apparatus, when standing on the proper plane, was to be touched 

 with that phial or conductor, it is evident, that either of them would impart to 

 it a quantity of its electricity, proportional to the plate's capacity, viz. so much 

 of it as should make the intensity of the electricity of the plate equal to that of 

 the electricity in the conductor or phial, suppose of half a degree ; but the 

 plate's capacity, now that it lies on the proper plane, is above 100 times greater 

 than if it stood insulated in the air, or, which is the same thing, it requires 100 

 times more electricity in order to show the same intensity ; therefore, in this 

 case it must require upwards of 100 times more electricity from the phial or 



* This explanation, properly applied, renders evident the actions of points in general. Properly 

 speaking, a pointed conductor, not insulated, when presented to an electrified body, has not in itself 

 any particular virtue of attracting electricity. It acts only like a conductor not insulated, which does 

 not oppose any resistance to the passage of the electric fluid. If the same conductor, instead of 

 being pointed, was to present a globular or flat surface, to the electrified body, neither would it in 

 that case oppose a greater resistance to the passage of the electricity. But the reason why the elec- 

 tricity will not pass nearly so easily from the electrified body to the conductor when it is flat or globu- 

 lar, as when it is pointed, is because in the former case the intensity of the electricity in the electri- 

 fied body is weakened by the opposed fiat surface, which, acquiring the contrary electricity, com- 

 pensates the diminished intensity incomparably more than a point can. It appears, therefore, that 

 it is not the particular property of a point or of a flat surface, but the different state of tin- electrified 

 body, that makes it part with its electricity easier, and from a greater distance, when a pointed con- 

 ducting substance, than when a flat or globular one is presented to it. — Orig. 



