To Jonathan Williams
Philadelphia. Jan. 15. 1800.
Th: Jefferson presents his compliments & thanks to mr Williams for the copy of his Thermometrical navigation which he was so kind as to send him. he has read it, as he had done before, in another form, with great satisfaction, and has no doubt it will be of great utility to navigators.
Th: J. has for some time wished he could try the thermometer daily in the river near which he lives, presuming it would furnish a very steady measure of the advance & recess of the seasons, and that such observations made in the rivers of different states would exhibit one of the good comparative views of climate. but the present course of his life forbids it. health and friendly salutations.
Williams’s recently published book was Thermometrical Navigation. Being a Series of Experiments and Observations Tending to Prove, that by Ascertaining the Relative Heat of the Sea-Water from Time to Time, the Passage of a Ship through the Gulph Stream, and from Deep Water into Soundings, May be Discovered in Time to Avoid Danger (Philadelphia, 1799; see Sowerby, description begins E. Millicent Sowerby, comp., Catalogue of the Library of Thomas Jefferson, Washington, D.C., 1952–59, 5 vols. description ends No. 649). In another form: the book incorporated reports that Williams and Benjamin Franklin, his great-uncle, had presented to the American Philosophical Society in 1785, 1790, and 1792 (APS description begins American Philosophical Society description ends , Transactions, 2 , 294–329; 3 , 82–100, 194–202).