181 



All bodies then, and all their component particles, when 

 in their natural situation, have round their surfaces, 

 where they are not in absolute contact with other sur- 

 faces, an imperceptible atmosphere, sufficient to balance 

 the smaller force with which they are attacked : every 

 way similar to the perceptible atmosphere of bodies 

 forcibly electrified. In these imperceptible atmospheres 

 is placed the power which resists their being electrified 

 to an higher degree than they are naturally. And this 

 power lies in ihe elasticity of the subtle fluid, every 

 where dispersed both round all bodies and in them* 



Glass is very difficulty electrified, which seems to 

 prove it has a very dense electric atmosphere. Metals 

 are easily electrified ; consequently they have rare, and 

 therefore weakly resisting atmospheres. But as heat 

 rarefies all bodies, so if glass be heated to a certain 

 degree, even below melting, it will give as free a passage 

 to the electric fire as brass or iron does : the atmosphere 

 round it being then rendered as rare as that of metals. 

 Nay, when melted, it makes no more resistance than . 

 water. But its resistance increases as it cools ; and 

 when it is quite cold it resists as forcibly as ever. 

 Smoothly-polished wax resists as much as glass. But 

 even the small heat raised by rubbing will render its 

 atmosphere as rare as that of metals, and so entirely 

 destroy its resistance. The same is true of rosin and 

 brimstone. Even the heat arising from friction destroys 

 the resistance which they naturally make to being, elec- 

 trified : a strong proof thai the resistance of all bodies 

 thereto, is exerted at their surfaces, and caused by an 

 electric atmosphere of different- densities, according to 

 their different circumstances, . 



Most experiments willsucceed as well with' a globe of 

 brimstone as with one of glass, Yet there is a consider- 

 able difference in their nature^ What glass repels, brim- 

 stone (as also rosin) attracts. Rubbed glass emits the 

 dectric fire : rubbed brimstone, rosin, and wax,, receive it* 

 Heace if a glass globe be turned at one end of a prime 

 i .6-' 



