on might convey intelligence to another inside.

This idea was perhaps the basis of the sympathetic telegraph of the
Middle Ages, which is first described in the MAGIAE NATURALIS of John
Baptista Porta, published at Naples in 1558. It was supposed by Porta
and others after him that two similar needles touched by the same
lodestone were sympathetic, so that, although far apart, if both
were freely balanced, a movement of one was imitated by the other.
By encircling each balanced needle with an alphabet, the sympathetic
telegraph was obtained. Although based on error, and opposed by Cabeus
and others, this fascinating notion continued to crop up even to the
days of Addison. It was a prophetic shadow of the coming invention. In
the SCEPSIS SCIENTIFICA, published in 1665, Joseph Glanvil wrote, 'to
confer at the distance of the Indies by sympathetic conveyances may
be as usual to future times as to us in literary correspondence.' [The
Rosicrucians also believed that if two persons transplanted pieces of
their flesh into each other, and tattooed the grafts with letters, a
sympathetic telegraph could be established by pricking the letters.]

Dr. Gilbert, physician to Queen Elizabeth, by his systematic researches,
discovered the magnetism of the earth, and laid the foundations of
the modern science of electricity and magnetism. Otto von Guericke,
burgomaster of Magdeburg, invented the electrical machine for generating
large quantities of the electric fire. Stephen Gray, a pensioner of
the Charterhouse, conveyed the fire to a distance along a line of pack
thread, and showed that some bodies conducted electricity, while others
insulated it. Dufay proved that there were two qualities of electricity,
now called positive and negative, and that each kind repelled the like,
but attracted the unlike. Von Kleist, a cathedral dean of Kamm, in
Pomerania, or at all events Cuneus, a burgher, and Muschenbroek, a
professor of Leyden, discovered the Leyden jar for holding a charge of
electricity; and Franklin demonstrated the identity of electricity and
lightning.

The charge from a Leyden jar was frequently sent through a chain of
persons clasping hands, or a length of wire with the earth as part of
the circuit. This experiment was made by Joseph Franz, of Vienna, in
1746, and Dr. Watson, of London, in 1747; while Franklin ignited spirits
by a spark which had been sent across the Schuylkill river by the same
means. But none of these men see