An 18th-century Gulf Stream chart by Franklin’s grand-nephew Jonathan Williams

Jonathan Williams, [Untitled map of the Atlantic Ocean and Gulf Stream.] [Philadelphia, 1793.]
Engraving, 7 ¾”h x 16 ½”w plus wide margins, uncolored. Some light foxing, one fold reinforced on verso, and a few tiny nicks and edge tears. A few annotations in pencil on verso. Very good overall.

A scarce and interesting 1793 chart depicting the Gulf Stream, as well as thermometric observations of the Atlantic made on several trans-Atlantic voyages by Jonathan Williams.

A grand-nephew of Benjamin Franklin, Jonathan Williams (1750-1815) served as his uncle’s personal secretary during his service as American agent in England in the early 1770s and as ambassador to France during the American Revolution. Williams later served in he U.S. Army as a senior military engineer, overseeing the fortification of New York Harbor. In 1801 President Jefferson appointed him as the first superintendent of the Military Academy at West Point, and in 1802 he received a concurrent appointment as commander of the newly-established Corps of Engineers.

Williams’ hydrographic interests developed during his time as Franklin’s secretary. Franklin made regular thermometric observations during his several trans-Atlantic voyages and was one of the first Americans to describe the Gulf Stream. He had first informed the world of his Gulf Stream findings in his paper “Maritime Observations” presented to the American Philosophical Society on December 2, 1785 and published in 1786 Volume II of the Proceedings. Franklin died in 1790, and Williams’ presented his follow-up paper to the Society on November 19 of that year.

“In the months of August and September, 1785 I was a fellow passenger with the late Doctor Franklin from Europe to America, and made, under his direction, the experiments mentioned in his description of the course of the gulph stream, an account of which was annexed to his maritime observations, and published in the Philosophical Transactions Vol. II. Page 328, I then determined to repeat these experiments in my future voyages.” (pp. 82-83)

Despite its significance, and the Franklin connection, Williams’ paper was only published in 1793, in Volume III of the Proceedings, under the title “On the Use of the Thermometer in Discovering Banks, Soundings, Etc.” The article was illustrated by the chart offered here, which the North Atlantic and adjacent areas of North America and Europe in outline. The course of the Gulf Stream is shown by shading, and dotted lines delineate the tracks of five trans-Atlantic voyages made by Williams, including the 1785 voyage on the London packet accompanying Franklin on his triumphant return from France. Flanking each track are numerous thermometric readings taken by Williams.

Williams’ core finding is that the water temperature tends to decline as one approached banks or shoals. This may be seen, for example, in the thermometric readings taken from the Chesterfield on its June 1790 voyage from England to Halifax, during which the sea temperature dropped significantly as the vessel approached the Grand Banks off Newfoundland. From this finding Williams infers that “by noticing the changes in the heat of the sea water, a navigator might always know when he is in soundings, and thereby be able to escape the dangers arising from unexpected currents, and erroneous reckoning.” (ibid.)

Per Wheat and Brun this is the first state of the chart, though a friend has brought to my attention the existence of an earlier state, lacking the binding instructions above the upper neat line. Wheat and Brun identify a “second” state (i.e., the third) with the shading for the Gulf Stream extended and directional arrows added, which appeared later in Williams’ Thermometrical Navigation (Philadelphia, 1799).

Wheat and Brun, Maps and Charts Published in America before 1800, #724. Background on early American Gulf Stream research may be found in Louis de Vorsey, “Pioneer Charting of the Gulf Stream,” Imago Mundi no. 28 (1976), pp. 105-120.


Engraving, 7 ¾”h x 16 ½”w plus wide margins, uncolored. Some light foxing, one fold reinforced on verso, and a few tiny nicks and edge tears. Some well-informed annotations to verso, showing through ever so slightly but affecting lower margin only. Very good overall.