4'2'2 PHILOSOPHICAL TRANSACTIONS. [aNNO 1753. 



cording to Mr. Franklin, excited glass emits the electrical fluid, but excited wax 

 receives it. 



Eip. 3. — Let a tin tube, of 4 or 5 feet in length, and about 2 inches in dia- 

 meter, be insulated by silk ; and from one end of it let the cork balls be sus- 

 pended by linen threads. Electrify it, by bringing the excited glass tube near 

 the other end, so as that the balls may stand an inch and a half, or 1 inches 

 apart : then, at the approach of the excited tube, they will by degrees lose their 

 repelling power, and come into contact ; and as the tube is brought still nearer, 

 they will separate again to as great a distance as before : in the return of the 

 tube they will approach each other till they touch, and then repel as at first. If 

 the tin tube be electrified by wax, or the wire of a charged phial, the balls will 

 be affected in the same manner at the approach of excited wax, or the wire of 

 the phial. 



Exp. 4. — Electrify the balls as in the last experiment by glass ; and at the ap- 

 proach of an excited stick of wax their repulsion will be increased. The effect 

 will be the same, if the excited glass be brought towards them, when they have 

 been electrified by wax. 



The bringing the excited glass to the end, or edge of the tin tube, in the 3d 

 experiment, is supposed to electrify it positively, or to add to the electrical fire it 

 before contained ; and therefore some will be running off" through the balls, and 

 they will repel each other. But at the approach of excited glass, which likewise 

 emits the electrical fluid, the discharge of it from the balls will be diminished ; or 

 part will be driven back, by a force acting in a contrary direction ; and they will 

 come nearer together. If the tube be held at such a distance from the balls, that 

 the excess of the density of the fluid round about them, above the common 

 quantity in air, be equal to the excess of the density of that within them, above 

 the common quantity contained in cork : their repulsion will be quite destroyed. 

 But if the tube be brought nearer ; the fluid without, being more dense than 

 that within the balls, it will be attracted by them, and they will recede from each 

 other again. 



When the apparatus has lost part of its natural share of this fluid, by the ap- 

 proach of excited wax to one end of it, or is electrified negatively ; the electrical 

 fire is attracted and imbibed by the balls to supply the deficiency ; and that more 

 plentifully at the approach of excited glass, or a body positively electrified, than 

 before ; whence the distance between the balls will be increased, as the fluid sur- 

 rounding them is augmented. And in general, whether by the approach or re- 

 cess of any body; if the difference between the density of the internal and external 

 fluid be increased, or diminished ; the repulsion of the balls will be increased, or 

 diminished, accordingly. 



Exp. 5. — When the insulated tin tube i» not electrified, bring the excited 



