Benjamin Franklin (1706-1790) noticed something odd as Deputy Postmaster General for the American colonies in London: mail took much longer travelling west across the Atlantic than it did travelling east. Several weeks longer, in fact. In a 1746 letter, Franklin ascribes this anomaly to an effect of the Earth’s rotation, making an eastward journey faster than a westward one. By 1762, Franklin is using the term ‘Gulph Stream’ to describe the “Trade Wind blowing over the Atlantic Ocean constantly…in a strong current.” In 1768, Franklin approached his cousin, Timothy Folger, captain of a Nantucket merchant vessel who had extensive knowledge of the coastal Atlantic waters. According to Folger, Nantucket whalers had cruised their ships along the edge of the Stream while hunting for whales and were already familiar with its patterns.Folger and Franklin jointly produced a chart of the Gulf Stream in 1768, first published in London by the English firm Mount and Page. The Geography and Map Division holds one of only three known copies of this first edition (see above), in addition to a copy of the ca.1785 second edition (see below). The second map, informally called the ‘Le Rouge edition’ is a French version of the Franklin-Folger chart, engraved by George-Louis le Rouge in Paris. The ‘Le Rouge edition’ was donated to The Library of Congress in 1935 by Franklin Bache, a direct descendant of Benjamin Franklin. While Franklin was the first man to formally name and chart the Gulf Stream, he was not the first to write about it. In 1513, Ponce de Leon recorded what we now consider the first written description of the Gulf Stream. He and his chief pilot, Antón de Alaminos, encountered the current while sailing from Puerto Rico to the east coast of Florida and noted how their three ships were consistently pushed by the current. None of Ponce de Leon’s original logs or maps are extant. However, Antonio de Herrera used Ponce de Leon’s logs as the basis of an early 17th century book he wrote describing the voyage, Historia General de los Hechos de los Castellanos en las Islas y Tierra Firme del Mar Oceano, published in Madrid, 1601-1615.
So what exactly is this “Trade Wind blowing over the Atlantic Ocean constantly”? The Gulf Stream is a powerful, wind-driven ocean current that transports vast amounts of low altitude heat to high altitude, cooler areas. This kind of heat transport by ocean currents prevents extreme temperature differences between equatorial and polar regions. Wind exerts a frictional force on surface water, so ocean currents tend to flow in similar patterns as the wind. Without this kind of global heat transport, the Atlantic Ocean could be home to much more intense mid-latitude cyclones and hurricanes.
If you’re interested in learning more about the history of the Gulf Stream, keep an eye out for a forthcoming Occasional Paper from our Division, “The History of the Gulf Stream’s Missing Chapter: John William Gerard De Brahm” by Louis De Vorsey.