Attach a small light _lock of cotton_ to the underside of the
prime conductor, so that it may hang down towards the pointed wire
mentioned in the first experiment. _Cover_ the point with your
finger, and the globe being turned, the cotton will extend itself,
stretching down towards the finger, as at _a_; but on _uncovering_
the point, it instantly flies up to the prime conductor, as at _b_,
and continues there as long as the point is uncovered. The moment
you cover it again, the cotton flies down again, extending itself
towards the finger; and the same happens in degree, if (instead of
the finger) you use, uncovered, the _blunt_ end of the wire uppermost.