From Thomas Jefferson to Dennis Griffith, 7 September 1793
To Dennis Griffith
Philadelphia Sep. 7. 1793.
Sir
I have duly received your favor of Aug. 31. and am sorry it is not in my power to give you any satisfactory answer, as the papers which served for my information in writing the Notes on Virginia were left in that state when I went to Europe and are still there. Ten or eleven years having elapsed since writing that work, and my mind totally withdrawn in the mean time to other objects, my memory does not enable me to say upon what information I stated the latitude of the dividing line of Virginia and Maryland on the Eastern shore. But I suspect it was on a Report from Commissioners appointed by Virginia to examine that boundary. I know there was such a report, and I either have it, or had the use of it, and I believe it was made either a little before or after the commencement of the Revolution war. The original must be in the office of the house of delegates of Virginia. A copy of it must be among the papers of the late Colo. G. Mason, who was too curious in things of this kind not to have had a copy of it. The difference between Mason and Dixon’s computation of a degree of Latitude, adopted by you, viz. 68.896 Miles (I take this from your letter and suppose it to be decimal notation) and Cassini’s which I adopted to wit 68 Miles—864 feet, or in miles and decimals of a mile 68.1636 miles would account for between one and two seconds of our variation.—Should you not have occasion to decide this matter before February or March next I shall be able to answer you from an inspection of my papers in Virginia, and will examine into it for you with pleasure. I am Sir Your most obedt. servt.
Th: Jefferson
PrC (DLC); at foot of text: “Mr. D. Griffith.” Tr (ViU: Edgehill-Randolph Papers); 19th-century copy.
On 10 Dec. 1777 the Virginia General Assembly appointed George Mason, Thomas Ludwell Lee, and James Henry Commissioners to meet with a delegation from Maryland “to adjust and confirm the rights of each, to the use and navigation of, and jurisdiction over, the bay of Chesapeake, and the rivers Potomac and Pocomoke.” No agreement was reached at this time, and the Virginia report which TJ consulted has not been found (, Oct. 1777, 1827 ed., p. 64–5, 73–4; Edward B. Mathews and Wilbur A. Nelson, Report on the Location of the Boundary Line along the Potomac River between Virginia and Maryland In accordance with The Award of 1877 [Baltimore, 1928], 3–4). TJ presumably obtained Cassini’s figure for the length of a degree of latitude from César François Cassini de Thury, Relation de deux Voyages Faits en Allemagne … Par Rapport a La Figure de la Terre, Pour déterminer la grandeur des degrés de longitude … (Paris, 1763). See No. 3806; Notes, ed. Peden, 3–4.