A NATION REALIZED 105In the summer of 1726 Benjamin Franklin was a
young man of twenty, sailing home to the colonies
after his first visit to London. As his ship approached
the North American coast, a wet hot wind picked up
and the water changed color to show an abundance
of grass and other marine life. At the same time, the
ship’s pace slowed considerably, though Franklin was
unable to account for any of these abrupt changes.
Twenty years later Franklin observed a similar
puzzle: ships sailing east seemed to move more
quickly across the Atlantic than those bound for
the American colonies. Franklin was drawn to this
problem for a third time another twenty years later,
but with greater urgency. In his capacity as Deputy
Postmaster General for the American colonies, he
heard from customs commissioners in Boston that
mail packets traveling from Falmouth in England
to New York were taking two weeks longer to arrive
than those sailing from London to Rhode Island,
even though the former trip was a shorter distance.
Franklin consulted his cousin, the experienced
navigator Timothy Folger, who speculated that the
packet ships heading to Rhode Island must have
been piloted by captains who understood the Gulf
Stream. Sailors had long known about this current
even though it had not been mapped or documented
in navigation or maritime guides.
Folger had learned of the Gulf Stream through
his experience among New England whalers. They
described a current that flowed up the coast from
Florida and then turned east, one powerful enough to
separate whaleboats from their larger ships. British
captains heading toward America were fearful of the
rocky shoals of George’s Bank (just east of Nantucket
Island on the map), so they often sailed further south
and thereby placed themselves directly against the
Gulf Stream, which was moving east. This could add
THE CURRENTS OF THE ATLANTIC WORLD
James Poupard and Benjamin Franklin,
“A Chart of the Gulf Stream,” 1786
days to their journey, and though they were often
warned as much by American whalers, their advice
was usually ignored.
Folger charted the basic dynamics of the current
for Franklin, showing him how it broadened and
narrowed. Franklin printed and distributed Folger’s
chart among British sea captains in 1769 or 1770 in
the hopes that they might use it to their advantage,
but the advice was (again) ignored. During the
Revolutionary War this maritime knowledge became
sensitive information, leading Franklin to stop
distributing the chart to British sailors. Once the
war ended, he published his own picture of the Gulf
Stream, shown here, in the Transactions of the American
Philosophical Society. The main map focuses on the
varied strengths of the current along the Atlantic
coast, while the inset depicts its entire course. In a
small cartouche at lower right Franklin stands on a
spit of land, sharing the map with Neptune. Engraved
by James Poupard, Franklin’s map was a hit, and by
the end of the 1780s the “Gulph Stream” had entered
the American lexicon.
While Franklin and Folger were researching this
current, William Gerard de Brahm was working in
the same vein. A migrant to the Georgia colony, de
Brahm noticed a current near the future site of Miami
while surveying the shoreline. In 1771 he sailed up
the coast to Newfoundland Bank, and then east
across the Atlantic. De Brahm published his own
chart of the Gulf Stream, which traced a current
moving along the North American coast before
joining others flowing south out of Hudson Bay and
the Saint Lawrence Seaway. Similarly, on this map
Folger and Franklin show the current moving along
the American coast before shifting south of George’s
Bank. De Brahm and Franklin were thus developing
the idea of the Gulf Stream at the same time, each
drawing on his own experience. Their initial charts
were published simultaneously about 1770, a
remarkable coincidence given that the current had
shaped European exploration, settlement, and trade
for over two centuries.