ctric," but he did not interpret the
phenomenon as electrical repulsion. Von Guericke, however, recognized
it as such, and refers to it as what he calls "expulsive virtue." "Even
expulsive virtue is seen in this globe," he says, "for it not only
attracts, but also REPELS again from itself little bodies of this sort,
nor does it receive them until they have touched something else." It
will be observed from this that he was very close to discovering the
discharge of the electrification of attracted bodies by contact with
some other object, after which they are reattracted by the electric.

He performed a most interesting experiment with his sulphur globe and a
feather, and in doing so came near anticipating Benjamin Franklin in
his discovery of the effects of pointed conductors in drawing off the
discharge. Having revolved and stroked his globe until it repelled a bit
of down, he removed the globe from its rack and advancing it towards the
now repellent down, drove it before him about the room. In this chase
he observed that the down preferred to alight against "the points of any
object whatsoever." He noticed that should the down chance to be driven
within a few inches of a lighted candle, its attitude towards the globe
suddenly changed, and instead of running away from it, it now "flew to
it for protection"--the charge on the down having been dissipated by
the hot air. He also noted that if one face of a feather had been first
attracted and then repelled by the sulphur ball, that the surface so
affected was always turned towards the globe; so that if the positions
of the two were reversed, the sides of the feather reversed also.

Still another important discovery, that of electrical conduction,
was made by Von Guericke. Until his discovery no one had observed the
transference of electricity from one body to another, although Gilbert
had some time before noted that a rod rendered magnetic at one end
became so at the other. Von Guericke's experiments were made upon
a linen thread with his sulphur globe, which, he says, "having been
previously excited by rubbing, can exercise likewise its virtue through
a linen thread an ell or more long, and there attract something." But
this discovery, and his equally important one that the sulphur ball
becomes luminous when rubbed, were practically forgotten until again
brought to notice by the discoveries of Francis Hauksbee and Stephen
Gray early in the eighteenth century. From this w