ectrical fire," but ever ready to give it up to any body
that has less. He explained the charged Leyden jar by showing that the
inner coating of tin-foil received more than the ordinary quantity of
electricity, and in consequence is POSITIVELY electrified, while the
outer coating, having the ordinary quantity of electricity diminished,
is electrified NEGATIVELY.

These studies of the Leyden jar, and the studies of pieces of glass
coated with sheet metal, led Franklin to invent his battery, constructed
of eleven large glass plates coated with sheets of lead. With this
machine, after overcoming some defects, he was able to produce
electrical manifestations of great force--a force that "knew no bounds,"
as he declared ("except in the matter of expense and of labor"), and
which could be made to exceed "the greatest know effects of common
lightning."

This reference to lightning would seem to show Franklin's belief, even
at that time, that lightning is electricity. Many eminent observers,
such as Hauksbee, Wall, Gray, and Nollet, had noticed the resemblance
between electric sparks and lightning, but none of these had more than
surmised that the two might be identical. In 1746, the surgeon, John
Freke, also asserted his belief in this identity. Winkler, shortly after
this time, expressed the same belief, and, assuming that they were
the same, declared that "there is no proof that they are of different
natures"; and still he did not prove that they were the same nature.

FRANKLIN INVENTS THE LIGHTNING-ROD

Even before Franklin proved conclusively the nature of lightning, his
experiments in drawing off the electric charge with points led to
some practical suggestions which resulted in the invention of the
lightning-rod. In the letter of July, 1750, which he wrote on the
subject, he gave careful instructions as to the way in which these rods
might be constructed. In part Franklin wrote: "May not the knowledge
of this power of points be of use to mankind in preserving houses,
churches, ships, etc., from the stroke of lightning by directing us to
fix on the highest parts of the edifices upright rods of iron made sharp
as a needle, and gilt to prevent rusting, and from the foot of these
rods a wire down the outside of the building into the grounds, or down
round one of the shrouds of a ship and down her side till it reaches the
water? Would not these pointed rods probably draw the electrical fire
silently out of a cloud befor