When the insulated tin tube is not electrified, bring the excited
glass tube towards the middle of it, so as to be nearly at right
angles with it, and the balls at the end will repel each other;
and the more so, as the excited tube is brought nearer. When it
has been held a few seconds, at the distance of about six inches,
withdraw it, and the balls will approach each other till they touch;
and then separating again, as the tube is moved farther off, will
continue to repel when it is taken quite away. And this repulsion
between the balls will be increased by the approach of excited
glass, but diminished by excited wax; just as if the apparatus had
been electrified by wax, after the manner described in the third
experiment.