manifestation of the same force that is produced when glass is
rubbed with buckskin. He invented the lightning rod, discovered
the phenomenon of positive and negative electricity, explained
the action of the Leyden jar, and was the first American writer
on the modern science of political economy. This energetic
citizen of Pennsylvania spent a large part of his life in
research; he studied the Gulf Stream, storms and their causes,
waterspouts, whirlwinds; and he established the fact that the
northeast storms of the Atlantic coast usually move against the
wind.

But Franklin was not the only scientist in the colony. Besides
his three friends, Kinnersley, Hopkinson, and Syng, who worked
with him and helped him in his discoveries, there were David
Rittenhouse, the astronomer, John Bartram, the botanist, and a
host of others. Rittenhouse excelled in every undertaking which
required the practical application of astronomy, He attracted
attention even in Europe for his orrery which indicated the
movements of the stars and which was an advance on all previous
instruments of the kind. When astronomers in Europe were seeking
to have the transit of Venus of 1769 observed in different parts
of the world, Pennsylvania alone of the American colonies seems
to have had the man and the apparatus necessary for the work.
Rittenhouse conducted the observations at three points and won a
world-wide reputation by the accuracy and skill of his
observations. The whole community was interested in this
scientific undertaking; the Legislature and public institutions
raised the necessary funds; and the American Philosophical
Society, the only organization of its kind in the colonies, had
charge of the preparations.