326 WRITINGS OF JOSEPH HENRY, [1855- 



charged surface; and for a similar reason, when the globe is 

 charged negatively, to draw in electricity from surrounding 

 bodies. 



From the second proposition, we can readily deduce the 

 fact of the distribution of the electricity at the surface ; for 

 if we communicate to the interior of a globe a quantity of 

 electricity just sufficient to arrange itself in a stratum of the 

 thickness of a single particle, it will so arrange itself on 

 account of the mutual repulsioh of the atoms, but if an 

 additional quantity is thrown into the interior, it might not 

 appear evident that this would also come to the surface, since 

 the repulsion of the atoms already at the surface, (as it would 

 seem at first sight,) would drive the additional atoms back 

 towards the centre; but from the second proposition, the 

 inner atoms are not affected by the outer, and consequently 

 they would separate from each other by their mutual re- 

 plusion, as if the latter did not exist, and arrange themselves 

 at the surface. 



That this should take place when the sphere is charged 

 with redundant electricity is not difiicult to understand; 

 but when a deficiency exists, the explanation has not 

 been thought as easy. If however we suppose a quan- 

 tity of the natural electricity drawn from the interior of 

 a solid globe, then the un-saturated matter in the centre of 

 the globe will act as a sphere, and draw into itself the elec- 

 tricity from around, and thus produce a hollow spbere of 

 attracting matter, which will again draw into itself the 

 natural electricity from around, and in this way, it must be 

 evident, the deficiency will finally come to exist at the sur- 

 face. 



These propositions, which as we shall see are of great im- 

 portance in the study of the theory of atmospheric electricity, 

 can be readily demonstrated experimentally. If we coat a 

 large hollow glass globe with tin foil, and insert through an 

 opening into it a delicate electroscope, consisting of two slips 

 of gold leaf suspended parallel to each other, (a small piece 

 of the covering of tin foil being removed at two points on 

 opposite sides to observe any effects produced within,) not 



