The Shifting Gulf Stream

American ships’ captains in the Atlantic appear to have caught on early to the steady northeast current along North America’s eastern coast and across to northern Europe. However, no one apparently mapped that whole current until the late 1760s, when Benjamin Franklin and his cousin, Nantucket captain Timothy Folger (shown here, courtesy of the Nantucket Historical Association), created and privately published the first chart of the Gulf Stream.

That map can be explored at the Library of Congress website. Franklin wanted to speed up mail delivery across the Atlantic by showing British captains how to avoid the current when sailing west. Apparently most captains ignored him.

Coming home to America in 1775 in bureaucratic disgrace after leaking Gov. Thomas Hutchinson’s letters, Franklin apparently took his supply of printed maps with him; none survived in Britain. For two centuries that printing was thought to be entirely lost, but then a couple of examples turned up in French archives. Either French captains saw more potential in them, or Franklin brought a few copies when he arrived in France as an American diplomat.

While in Paris, Franklin allowed another map to be engraved. Yesterday I described how the Norman B. Leventhal Map Center at the Boston Public Library discovered Franklin’s own copy in its collection. That map’s labels are in French, and they suggest the Gulf Stream points to France, not Britain—emphasizing natural ties between the new allies?

On returning to the U.S. of A., Franklin commissioned yet another engraving of the Gulf Stream chart, this time published in Philadelphia by his American Philosophical Society in 1786. Here’s the Library of Congress’s image. This map’s inset shows all of western Europe equally, but this time the main map offers a lot more detail about the enticing Northwest Territory.

Thus, though the Gulf Stream doesn’t change much from one of Franklin’s maps to another, the lands shown around it change significantly.