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fulphur, amber, or a tube of glafs with the polijh 
taken off by emery ; its electricity will b q pofftive : 
whereas, if it be excited, fingly, or together with 
a white ribband, by drawing them brifkly between 
the fingers, it is always negative . Laying it on 
the paper, and drawing over its furface a rod, or 
tube of finooth glafs, its ele&ricity will alfo be 
negative. 
EXPERIMENT II. 
If a plate of glafs, ten, or twelve inches in dia- 
meter, be excited, and placed upon the top of a 
box, from which a pair of light pith or cork-balls 
are fufpended, being mounted on a fland of feal- 
ing-wax ; the balls will feparate, and fcand re- 
pelled from each other, being electrified pofi- 
tively, (in a dry air), upwards of four hours. 
When they come into contact, on removing the 
glafs, they diverge again, and are negatively elec- 
trified ; but, on replacing it, they clofe. On re- 
moving it again, they feparate ; and thus alter- 
nately as long as any electricity remains in it (e K 
If the plate of glafs be placed in a frame 
of wood, and a light pith or cork-ball be laid on 
its furface ; on prefenting towards it the end of a 
finger, or the point of a pin, &c. the ball will re- 
cede from them, with a very brifk motion, and 
may thus be driven about upon the furface of the 
glafs, like a feather in the air, by an excited tube, 
or the wire of a charged bottle. The cork-ball, 
(e) For an explanation of thefe phaenomena, fee Mr. can- 
ton’s experiments, Phiiofophical Tranfa&ions, Vol. LVIIL 
Part I. N° 53. 
being 
