ELECTRICAL PROPERTIES OF SILK. 
Tux distinction between those bodies which are 
capable of being excited to electricity, and those 
which are only capable of receiving it from the 
others, appears scarcely to have been even sus- 
pected till about the year 1729, when this great 
discovery was made by Mr Gray, a pensioner in 
the Charter-House. After some fruitless attempts 
to make metals attractive by heating, rubbing, and 
hammering, he conceived a suspicion, that, as a 
glass tube, when rubbed in the dark, communi- 
cated its light to various bodies, it might possibly, 
at the same time, communicate its power of at- 
tracting to them. In order to put this to the 
test, he provided himself with a tube three feet 
five inches long, and near an inch and one-fifth in 
diameter ; the ends of the tube were stopped by 
cork ; and he found that, when the tube was ex- 
cited, a down feather was attracted as powerfully 
by the cork as by the tube itself. To convince 
himself more completely, he procured a small ivory 
ball, which he fixed at first to a stick of fir, four 
inches long, which was thrust into the cork, and 
found that it attracted and repelled the feather even 
