tions.

His active, inquiring mind played upon hundreds of questions in a dozen
different branches of science. He studied smoky chimneys; he invented
bifocal spectacles; he studied the effect of oil upon ruffled water;
he identified the "dry bellyache" as lead poisoning; he preached
ventilation in the days when windows were closed tight at night, and
upon the sick at all times; he investigated fertilizers in agriculture.
Many of his suggestions have since borne fruit, and his observations
show that he foresaw some of the great developments of the nineteenth
century.

His fame in science rests chiefly upon his discoveries in electricity.
On a visit to Boston in 1746 he saw some electrical experiments and at
once became deeply interested. Peter Collinson of London, a Fellow
of the Royal Society, who had made several gifts to the Philadelphia
Library, sent over some of the crude electrical apparatus of the day,
which Franklin used, as well as some contrivances he had purchased in
Boston. He says in a letter to Collinson: "For my own part, I never was
before engaged in any study that so engrossed my attention and my time
as this has lately done."

Franklin's letters to Collinson tell of his first experiments and
speculations as to the nature of electricity. Experiments made by a
little group of friends showed the effect of pointed bodies in drawing
off electricity. He decided that electricity was not the result of
friction, but that the mysterious force was diffused through most
substances, and that nature is always alert to restore its equilibrium.
He developed the theory of positive and negative electricity, or plus
and minus electrification. The same letter tells of some of the tricks
which the little group of experimenters were accustomed to play upon
their wondering neighbors. They set alcohol on fire, relighted candles
just blown out, produced mimic flashes of lightning, gave shocks
on touching or kissing, and caused an artificial spider to move
mysteriously.

Franklin carried on experiments with the Leyden jar, made an electrical
battery, killed a fowl and roasted it upon a spit turned by electricity,
sent a current through water and found it still able to ignite alcohol,
ignited gunpowder, and charged glasses of wine so that the drinkers
received shocks. More important, perhaps, he began to develop the theory
of the identity of lightning and electricity, and the possibility of
protecting buildings by iron rods.