Thomas Jefferson Papers

To Thomas Jefferson from Jonathan Williams, 22 May 1802

From Jonathan Williams

Mount Pleasant near Philadelphia May 22. 1802


After having ascertained by repeated Experiments that the Coast of America, and the eminences of Land upon it can be discovered by the varied Temperature of the Sea; it became a very natural suggestion that by a judicious use of the Thermometer a correct Chart might be made, which would not only be usefull to mariners by indicating soundings, when they could not heave the Lead; but to Society at large by discovering Fishing Banks, at present perhaps unknown.—To do this effectually would require a cruising Voyage, under the direction of an able Astronomer and draftsman accustomed to make Philosophical Experiments, from the Capes of Florida to Nova Scotia, and within the Gulph Stream; But such a Voyage, for such an Object, is not within the Power of any individual: To Government it would only be a particular direction to an ordinary Cruiser, & occasion no extraordinary Expence.

Now that the President of the Philosophical Society, and The Cheif Magistrate of the Union are in one person, I may without hazard of impropriety submit this suggestion to your Opinion: The apprehension however of exposing myself, to an imputation of vanity on a subject which may in some respects be considered as personal, would probably have prevented this communication if I had not received the inclosed Letter from an experienced french mariner, who has been some time settled on the north River, but who is about returning to France. This declaration that he will apply to the french Government for a Cruizer to perform this service to Humanity, if we do not, renders it a Duty in me, at least to lay his Letter before you.—The Consideration of your many & important employments during the session, is the only reason that I did not make the communication immediately.

When I last had the honour of seeing you I mentioned a magnetic oddity. I have by repeated experiment found it to be still more odd, for the experiment will not be the same with one bar of Iron that has been some time in a vertical Position, & another that has been lying in a horizontal position during a long time. The former will retain its polarity, for some time when lying down, tho’ it will not be so strong as when erect; the latter will have no polarity at all (unless in a North & South direction) when in a horizontal position; but will in an instant possess that quality if put in a vertical position. The Distance from Pole to Pole in the same Bar is very irregular, & varies from two feet to two Inches: A Bar of steel will retain its Polarity in all positions.

I have the honour to be with the greatest Deference & Respect Sir Your faithfull & obedient Servant

Jona Williams

RC (DLC); at foot of text: “Thomas Jefferson Esqr President of the American Philosophical Society”; endorsed by TJ as received 30 May and so recorded in SJL. PrC (InU: Jonathan Williams Manuscripts). Enclosure: Eugène Linet to Williams, 16 Feb. 1802; Linet has read Williams’s Thermometrical Navigation and states that using temperature readings to aid navigation “will certainly prove of the highest importance & of more universal benefit to Navigators than any operation made use of to rectify their reckoning on the approach of land”; shipwrecks are common on the coast of North America because, in part, of navigational errors caused by currents; the coast is also along “a parallel of Longitude,” and most captains are unable to calculate longitude to help them know when they are approaching land; because the water along this coast becomes shallow at a steep rate, it is possible when a ship is pushed by “a good breeze” to come up on a shore only hours after finding no bottom by the use of a sounding line; the ability to ascertain the direction of currents by water temperatures would alone make a great contribution to navigation; he recommends that a cruise be made to take observations and conduct experiments along the entire coast; since an American made the discovery of thermometrical navigation, the United States government should make that survey, but if that government should decline, Linet is confident that the first consul of France would authorize a voyage for the purpose; in closing, Linet asks if Williams’s work has been translated into French, expressing an interest in undertaking the task himself (DLC).

ASCERTAINED BY REPEATED EXPERIMENTS: Williams first collected readings of water temperature under the direction of his uncle, Benjamin Franklin, on a voyage from Europe to America in 1785. Data that Williams collected on subsequent voyages confirmed Franklin’s idea that the Gulf Stream was warmer than the ocean to either side of it and convinced Williams that water temperature could also help seafarers locate coasts, icebergs, and submerged banks and rocks. He submitted a paper and supplementary data to the American Philosophical Society in 1790. Seeing that report in the society’s Transactions prompted William Strickland to make temperature readings on trips from Hull to New York in 1794 and from Philadelphia to Falmouth in 1795. Strickland passed the results of his observations along to Williams, who transmitted them to the APS for publication. Williams compiled his views and findings under the title Thermometrical Navigation, which he published in 1799 and sent to TJ early the following year (APS, Transactions, 3:82–100; 5:90–103; Louis De Vorsey, “Pioneer Charting of the Gulf Stream: The Contributions of Benjamin Franklin and Willam Gerard De Brahm,” Imago Mundi, 28 [1976], 109–11; Vol. 31:308).

NORTH RIVER: the Hudson (Jedidiah Morse, The American Gazetteer, 2d ed. [Charlestown, Mass., 1804]).

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