1052. Mr. henly’s Obfervations 
ball inftantly comes to the fide of the glafs, and there re- 
mains fome feconds, and then returns to the center of 
the phial. Withdraw now the excited eleCtric, and the 
ball inftantly returns to the glafs upon the principle be- 
fore mentioned, which is more completely fhewn by the; 
filings in the little box.. 
JE X P X RIM E N TK- 
Let a piece of thin glafs be placed as a cover to a 
circular box, about fix inches in diameter, and three 
quarters of an inch deep: put into the box twenty 
or thirty light balls of cork, or of the pith of elder; 
then, having made the glafs very dry and warm, expofe 
the furface of it to the eleCtric 'matter ifluing from the 
prime conductor to a. good electrical machine, the balls 
will be inftantly in motion, and will fo continue for fome 
time, the box being moved in fuch manner that every 
part of the glafs may be affeCted. Then remove the 
box, and the balls being at reft, turn the glafs, placing 
the upper furface downward ; the balls will then inftantly 
renew their motion. When this fecond motion ceafes, 
touch the furface of the glafs near the center with a 
finger,, or, which is better, with a round, fmooth piece 
of 
