Lay two books on two glasses, back towards back, two or three inches
distant. Set the electrified phial on one, and then touch the wire;
that book will be electrified _minus_; the electrical fire being
drawn out of it by the bottom of the bottle. Take off the bottle, and
holding it in your hand, touch the other with the wire; that book
will be electrified _plus_; the fire passing into it from the wire,
and the bottle at the same time supplied from your hand. A suspended
small cork-ball will play between these books till the equilibrium is
restored.