CONCLUSIONS FROM THE PRECEDING INQUIRIES. 



241 



that the weight requisite to balance the force exerted between two equal spheres at 

 given distances may be invariably predicted with extraordinary precision. 



The following Table exhibits the results of a few experiments with two equal 

 spheres, obtained by the method already given (19.), the radius of the spheres being 

 each = one inch. 



73. With a view of verifying the above results, I obtained two circular areas, each 

 equal to the area of the given hemisphere expanded into a plane : these were opposed 

 as before, and were placed at the distances q q given in the above Table, so as to pass 

 through the points q q\ The experiments being repeated with the planes, the attrac- 

 tive forces were extremely near those deduced by the hemispheres ; indeed, upon a 

 mean of five observations for each distance, there did not arise any sensible dif- 

 ference. 



The various planes, spheres, and other conductors employed, were constructed of 

 light wood, neatly covered with gold-leaf: those intended to be suspended from the 

 balance were made hollow. I repeated the experiments with the electrometer B, 

 fig. 2, and arrived at similar results. 



74. Upon a due consideration of these, and the preceding experiments in air of 

 diminished density, we are led to conclusions of no inconsiderable consequence to our 

 views of electrical action. By the latter, (45.), it is demonstrated, that the resistance of 

 the air to the passage of electricity, is as the square of the density directly, so that a 

 given quantity, having a given intensity, and about to discharge or flow upon a given 

 point, will remain in the same relative state in air of half the density, if the distance 

 between the points of discharge be doubled (44. /.) ; or generally, if as the density of 

 the air be decreased, the distance between the points of action be increased, the elec- 

 trical accumulation will still remain complete. If, therefore, the density of the air be 

 indefinitely diminished, and the distance between the points of action indefinitely in- 

 creased, we shall have eventually the same relative electrical state continued, without 

 dissipation; so that if we imagine the opposed body c, fig. 17, to become nothing, then 

 the accumulated electricity will not tend to leave the electrified body c at all, sup- 

 posing it to be without the influence of all other substances. Discharges of electricity 

 under a diminished atmospheric pressure, therefore, do not seem to occur so much in 

 consequence of a tendency of the electric principle to evaporate, as it were, in all 

 directions into space, but rather in consequence of the removal of the non-conducting 



