640 I'HILOSOPHICAL TRANSACTIONS. [aNNO 1734. 



5. He suspended a child on silk lines, and made all the surprising experiments 

 described by Mr. Gray, Philos. Trans. N°417. But having tried the experi- 

 ment on his own body in the same manner, he observed several things very re- 

 markable. First, when he takes the paste-board or stand, on which the leaf- 

 gold is laid, into his hand, neither his other hand nor his face has any attrac- 

 tion. But if another person, who is in the chamber, comes near him, he will 

 attract it with his face, his hand, or even with a stick. 2. While he is sus- 

 pended on the lines, if the electric tube be put near one of his hands, or his 

 legs, and then if another person approach, and pass his hand within an inch 

 or thereabouts of his face, legs, hand, or clothes, there immediately issues 

 from his body one or more pricking shoots, with a crackling noise, that causes 

 to that person, as well as to M. Du Fay a little pain, resembling that from the 

 sudden prick of a pin, or the burning from a spark of fire, which is as sensibly 

 felt through the clothes, as on the bare hand or face. And in the dark these 

 snappings are, as may be easily imagined, so many sparks of fire. These snap- 

 pings, or sparks, are not excited, if a bit of wood, cloth, or any other substance 

 than a living body, be passed over the person suspended on the lines, unless it 

 be a piece of metal, which produces very nearly the same effect. Any other 

 living animal does the same, if put on the lines, and that first the tube, and 

 then the hand be applied near it: but it is otherwise, if the experiment be made 

 with the carcase of an animal ; for then one perceives only, if it be in the dark, 

 a still uniform light, without snappings or sparks. 



6. On making the experiment related by Otho de Guerik, in his collection of 

 experiments de Spatio Vacuo, which consists in making a ball of sulphur 

 rendered electrical, to repel a down-feather, M. Du Fay perceived that the 

 same effects were produced not only by the tube, but by all electric bodies 

 whatever ; and he discovered a very simple principle, which accounts for a great 

 part of the irregularities, and if he may use the term, of the caprices that seem 

 to accompany most of the experiments on electricity. This principle is, that 

 electric bodies attract all those that are not so, and repel them as soon as they 

 are become electric, by the vicinity or contact of the electric body. Thus leaf- 

 gold is first attracted by the tube; and acquires an electricity by approaching it; 

 and of consequence is immediately repelled by it. Nor is it re-attracted, while 

 it retains its electric quality. But if, while it is thus sustained in the air, it 

 chance to light on some other body, it presently loses its electricity ; and 

 consequently is re-attracted by the tube, which, after having given it a new 

 electricity, repels it a second time ; which continues as long as the tube keeps 

 its electricity. On applying this principle to the various experiments of electri- 

 city, one is surprised at ttie number of obscure and puzzling facts it clears up. 

 For Mr. Hauksbee's famous experiment of the glass globe, in which silk threads 



