The Philadelphia experiments and observations on electricity, as led and
communicated by Benjamin Franklin,1
were important in the history of science because
some were new and novel and because their interpretations helped to stimulate the
development of electricity as a science and the beginnings of modern physics.2-4 This
work also led to the sentry box and kite experiments5
that proved once and for all that
thunderclouds are electrified and that lightning is an electrical discharge. The latter
discoveries, in turn, validated the key assumptions that lay behind Franklin’s supposition
that tall, grounded rods would protect structures from lightning damage. Here, we will
trace how Franklin’s ideas evolved and the design of the first protective rods, and then we
will describe some key improvements that Franklin made to his design, after experience
was gained through practice in the years from 1752 to 1762.