630 PHILOSOPHICAL TRANSACTIONS. [aNNO 1755. 



but remain separate, and repel each other. This is plainly seen in suspended 

 cork balls, and other bodies electrified. 



2. An electric atmosphere not only repels another electric atmosphere, but 

 will also repel the electric matter contained in the substance of a body approach- 

 ing it ; and, without joining or mixing with it, force it to other parts of the 

 body, that contained it. This is shown by some of the following experiments. 



3. Bodies electrified negatively, or deprived of their natural quantity of elec- 

 tricity, repel each other, (or at least appear to do so, by a mutual receding) as 

 well as those electrified positively, or which have electric atmospheres. This is 

 shown by applying the negatively charged wire of a phial to two cork balls, sus- 

 pended by silk threads, and by many other experiments. 



Preparation. — Fix a tassel of 15 or 20 threads, 3 inches long, at one end of 

 a tin prime conductor ; (mine is about 5 feet long, and 4 inches diameter) sup- 

 ported by silk lines. Let the threads be a little damp, but not wet. 



Exper. 1 . — Pass an excited glass tube near the other end of the prime con- 

 ductor, so as to give it some sparks, and the threads will diverge. — Because each 

 thread, as well as the prime conductor, has acquired an elastic atmosphere, which 

 repels, and is repelled by, the atmospheres of the other threads : if those several 

 atmospheres would readily mix, the threads might unite, and hang in the middle 

 of one atmosphere, common to them all. 



Rub the tube afresh, and approach the prime conductor with it, crossways, 

 near that end, but nigh enough to give sparks ; and the threads will diverge a 

 little more. Because the atmosphere of the prime conductor is pressed by the 

 atmosphere of the excited tube, and driven towards the end where the threads 

 are, by which each thread acquires more atmosphere. 



Withdraw the tube, and they will close as much. — They close as much, and 

 no more, because the atmosphere of the glass tube, not having mixed with the 

 atmosphere of the prime conductor, is withdrawn entire, having made no addition 

 to, or diminution from, it. 



Bring the excited tube under the tuft of threads, and they will close a little. 

 — They close, because the atmosphere of the glass tube repels their atmospheres, 

 and drives part of them back on the prime conductor. 



Withdraw it, and they will diverge as much. — For the portion of atmosphere, 

 which they had lost, returns to them again. 



* Exper. 2. — Excite the glass tube, and approach the prime conductor with it, 

 holding it across, near the opposite end, to that on which the threads hang, at 

 the distance of 5 or 6 inches. Keep it there a few seconds, and the threads of 

 the tassels will diverge. Withdraw it, and they will close. — They diverge, be- 

 cause they have received electric atmospheres from the electric matter befor6 



