VOL. XLVIII.] PHILOSOPHICAL TRANSACTIONS. 423 



glass tube towards the middle of it, so as to be nearly at right angles with it, 

 and the balls at the end will repel each other ; and the more so, as the excited 

 tube is brought nearer. When it has been held a few seconds, at the distance 

 of about 6 inches, withdraw it, and the balls will approach each other till they 

 touch ; and thfen separating again, as the tube is moved farther off, will continue 

 to repel when it is taken quite away. And this repulsion between the balls will 

 be increased by the approach of excited glass, but diminished by excited wax ; 

 just as if the apparatus had been electrified by wax, after the manner described in 

 the 3d experiment. 



Exp. 6. — Insulate 2 tin tubes, distinguished by A and b, so as to be in a line 

 with each other, and about half an inch apart; and at the remote end of each 

 let a pair of cork balls be suspended. Towards the middle of A, bring the excited 

 glass tube ; and holding it a short time, at the distance of a few inches, each 

 pair of balls will be observed to separate ; withdraw the tube, and the balls of A 

 will come together, and then repel each other again ; but those of b will hardly 

 be affected. By tbe approach of the excited glass tube, held under the balls of 

 A, their repulsion will be increased : but if the tube be brought, in the same 

 manner, towards the balls of b, their repulsion will be diminished. 



In the 5th experiment, the common stock of electrical matter in the tin tube 

 is supposed to be attenuated about the middle, and to be condensed at the ends, 

 by the repelling power of the atmosphere of the excited glass tube, when held 

 near it. And perhaps the tin tube may lose some of its natural quantity of the 

 electrical fluid, before it receives any from the glass ; as that fluid will more 

 readily run off from the ends or edges of it, than enter at the middle : and ac- 

 cordingly, when the glass tube is withdrawn, and the fluid is again equally dif- 

 fused through the apparatus, it is found to be electrified negatively : for excited 

 glass brought under the balls will increase their repulsion. 



In the 6th experiment, part of the fluid driven out of one tin tube enters the 

 other ; which is found to be electrified positively, by the decreasing of the repul- 

 sion of its balls, at the approach of excited glass. 



Exp. 7- — Let the tin tube, with a pay- of balls at one end, be placed 3 feet at . 

 least from any part of the room, and the air rendered very dry by means of a fire: 

 electrify the apparatus to a considerable degree ; then touch the tin tube with a 

 finger, or any other conductor, and the balls will still continue to repel each 

 other ; though not at so great a distance as before. 



The air surrounding the apparatus to the distance of 2 or 3 feet, is supposed 

 to contain more or less of the electrical fire, than its common share, as the tin 

 tube is electrified positively, or negatively ; and when very dry, may not part 

 with its overplus, or have its deficiency supplied so suddenly, as the tin ; but 

 may continue to be electrified, after that has been touched, for a considerable time. 



