^**~s^t* t 



ELECTRICITY. 



held be increased, if it can be demonstrated, contrary to what has been gener- 

 ally maintained by the historians of the science, that to him is justly owing the 

 honor of the discovery of this physical principle ! 



Some of the more obvious phenomena of induction were noticed so early in 

 the progress of electrical science as the researches of Mr. Grey ; and many 

 other effects proceeding from it presented themselves to subsequent experi- 

 mental inquiries, but attracted no attention, and led to no consequences. Tho 

 first series of experiments, conducted so as to develop in an unequivocal man- 

 ner this principle, were laid before the Royal Society by Canton, on the Gth 

 of December, 1753.* They consisted chiefly in rendering insulated conduc- 

 tors electrical, by bringing near to one end an excited glass tube, or stick of 

 wax, and exhibiting the varying state of cork-balls suspended on the conductor 

 by the alternate approach and removal of the excited electric. 



These experiments having been communicated to Franklin, he pursued the 

 inquiry, and succeeded in expressing, in clear and unequivocal terms, the prin- 

 ciple of induction ; that is to say, in demonstrating that a body charged with 

 either kind of electricity will, on approaching a conductor in its natural state, 

 render that part of such conductor which is nearest to it electrical ; that its 

 electricity will be contrary to that of the approaching electrified body ; that on 

 removing the electrified body, the conductor would be restored to its natural 

 ftate : all which effects Franklin showed would follow from his theory, by as- 

 suming that the electric fluid is self-repulsive, and attracted by the matter of 

 the conductor. 



The experiments and reasoning which appear to establish Franklin's right 

 to the honor of this discovery are so concise, that they may be stated here 

 nearly in his own words. 



Let a metallic conductor, about five feet long and four inches in diameter, 

 be suspended by dry silk lines, so as to be insulated. From one end of it sus- 

 pend a tassel consisting of fifteen or twenty threads in a damp state, so as to 

 give them a conducting power. Present an electrified glass tube within five 

 or six inches of the opposite end, and keep it in that position for a few sec- 

 onds. The threads of the tassel will diverge, and when the tube is withdrawn 

 they will collapse. 



While the tube is held near the opposite end of the conductor and the 

 threads are divergent, present the finger to the end of the conductor at which 

 the tassel is suspended. A spark will be received, and the threads of the 

 tassel will collapse. 



Let the tube be then removed. The threads of the tassel will again di- 

 Terge. 



Let the tube be again presented as before. The threads will again collapse, 

 and so on. 



Finally, let the tube be presented to the tassel. The divergence of the 

 threads will immediately increase, and continue to increase, as the tube is 

 brought nearer to the tassel. 



These phenomena are accounted for by Franklin in the following manner: 

 ' By taking the spark from the end of the conductor, you rob it of part of its 

 natural quantity of electrical matter, which part so taken away is not supplied 

 by the glass tube, and the conductor remains negatively electrified. On with- 

 drawing the tube, the electric matter on the conductor recovers its equilibrium, 

 or equal diffusion ; and the conductor having lost some of its natural luctricity, 

 the threads connected with it lose part of theirs, and so are electriiiod nega- 

 tively, and repel each other. 



Phil. Trana., vol. xlviii., p. 350. 



