PROGRESS IN ELECTRICITY 



plain it satisfactorily. Dufay, repeating Von Guericke's 

 experiments, found that if, while the excited tube or 

 sulphur ball is driving the repelled feather before it, 

 the ball be touched or rubbed anew, the feather comes 

 to it again, and is repelled alternately, as the hand 

 touches the ball, or is withdrawn. From this he con- 

 cluded that electrified bodies first attract bodies not 

 electrified, "charge" them with electricity, and then 

 repel them, the body so charged not being attracted 

 again until it has discharged its electricity by touching 

 something. 



"On making the experiment related by Otto von 

 Guericke," he says, "which consists in making a ball 

 of sulphur rendered electrical to repel a down feather, 

 I perceived that the same effects were produced not 

 only by the tube, but by all electric bodies whatso- 

 ever, and I discovered that which accounts for a great 

 part of the irregularities and, if I may use the term, of 

 the caprices that seem to accompany most of the experi- 

 ments on electricity. This principle is that electric 

 bodies attract all that are not so, and repel them as 

 soon as they are become electric by the vicinity or 

 contact of the electric body. Thus gold-leaf is first 

 attracted by the tube, and acquires an electricity by 

 approaching it, and of consequence is immediately 

 repelled by it. Nor is it reattracted 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 

 straightway loses its electricity, and in consequence is 

 reattracted 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. Upon apply- 



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