Note: this document has content that may require expanded/print view for best results (icons above right)

Thomas Jefferson’s Notes on the Latitude of Willis’s Mountain, [ca. 19 December 1811]

Notes on the Latitude of Willis’s Mountain

[ca. 19 Dec. 1811]

Latitude of Willis’s mountain by observations of the Sun’s meridian altitude taken from the peak on the right side of the gap, & next adjacent to it, as seen from Monticello.

				º		′		″
1811.	Nov.	21.	Meridian alt. of ☉ by observn*	32	–	37	–	20	1
	Dec.	18.		29	–	2	–	50	2
		19		29	–	4	–	50	3

the 1st by Th:J. the 2. last by Th:J.R.

other elements for the calculation.

Willis’s mountains being 62.′ E. of the South as seen from Monto and 40.5 common miles distant, it’s meridian will be .72136 of a mile E. of yt of Monticello. a degree of longitude in Lat. 37º–30′ = 47.6 geogr. mi. = 54.74 com. miles then .72136 of a common mile = 47.4″6 of longitude

	º		′		″
which subtracted from ye long. of Monto	78	–	50	–	18.877
gives diffce of long. betw Greenwich & W’s M.	78	–	49	–	31.477

											º		′		″
Nov. 21.	☉’s meridian altitude by observn										32	–	37	–	207
		′		″
	– refraction	1	–	29
	+ parallax			8									1	–	21
	true Alt. of ☉’s center										32	–	35	–	598
											90	–
	Zenith distance										57	–	24	–	19

					º		′		″
	☉’s decln at Greenwich				19	–	48	–	13
	increase for 78º– 50′– 19″10						2	–	48.8		19	–	50	–	56
											37	–	33	–	5

Dec.11 18.	☉’s merid. alt. by observn
											°		′		″
		′		″						*	29	–	2	–	50
	– refraction	1	–	42
	+ parallax			8									1	–	34
	true alt. of ☉’s center										29	–	1	–	16
											90	–
	Zenith distance										60	–	58	–	44

					°		′		″
	☉’s decln Greenwich				23	–	23	–	34
	increase for 78º– 50′– 19″12							–	17		23	–	23	–	34
											37	–	35	–	1013

Dec. 19.	Merid. Alt. of ☉ by observn									†	29	–	4	–	5014
		′		″
	– refraction	1	–	42
	+ parallax			8									1	–	34
	true alt. of ☉’s center.										29	–	3	–	1615
											90	–
	Zenith distance										60	–	56	–	4416

					°		′		″
	☉’s decln at Greenwich				23	–	25	–	18
	increase for 78º– 50′– 19″17							–	11		23	–	25	–	29
	Lat. of Willis’s Mountain										37	–	31	–	1518

Th:J.R’s observn of Dec.	18. gives Lat.						37	–	35	–	1019
	19.						37	–	31	–	1520
							75	–	6	–	2521
	mean						37	–	33	–	12.5 22
Th:J’s observation Nov. 21. gives							37	–	33	–	523
	difference										7.5″
Lat. of Monticello		38	–	8
W’s Mountn		37	–	33	–	5
difference				34	–	55	= 40.15 miles

MS (Roger W. Barrett, Chicago, 1947); written entirely in TJ’s hand on both sides of a single sheet; undated.

On 20 Nov. 1811 TJ was at Mill Brook, the residence of his son-in-law John Wayles Eppes, located in eastern Buckingham County about three miles from Willis’s Mountain. He was staying at Poplar Forest on 18 and 19 Dec. 1811 (MB description begins James A. Bear Jr. and Lucia C. Stanton, eds., Jefferson’s Memorandum Books: Accounts, with Legal Records and Miscellany, 1767–1826, 1997, The Papers of Thomas Jefferson, Second Series description ends , 2:1271, 1272).

th:j.r.: Thomas Jefferson Randolph. The geographical (geogr.) mile is defined as one minute of arc along the equator, or approximately 1,850 meters (OED description begins James A. H. Murray, J. A. Simpson, E. S. C. Weiner, and others, eds., The Oxford English Dictionary, 2d ed., 1989, 20 vols. description ends ).

1. Reworked from “32–35–40.”

2. Reworked from “29–2–10.”

3. Reworked from “29–3–10.”

4. TJ here canceled “observn.”

5. Reworked from “35.”

6. Reworked from “45.”

7. Reworked from “32–35–40.”

8. Reworked from “32–34–19.”

9. Reworked from “57–25–41.”

10. Reworked from “78°–34′–20″.”

11. Verso begins with this word.

12. Reworked from “78°–34′–20″.”

13. Reworked from “37–36–30.”

14. Reworked from “29–3–10.”

15. Reworked from “29–1–36.”

16. Reworked from “60–58–24.”

17. Reworked from “78°–34′–20″.”

18. Reworked from “37–32–55.”

19. Reworked from what appears to be “37–37–13.”

20. Reworked from what appears to be “37–32–15.”

21. Reworked from “75–9–28.”

22. Reworked from “37–34–14.”

23. Reworked from “37–32–[ ].”

Authorial notes

[The following note(s) appeared in the margins or otherwise outside the text flow in the original source, and have been moved here for purposes of the digital edition.]

*	°		′
	65	–	18
–			3	–	20	error of4 instrument
	65	–	14	–	40
÷ 2	32	–	37	–	20

*	°		′
	58	–	9			by the instrumt
–			3	–	20	error of instrumt
	58	–	5	–	40
÷ 2.	29	–	2	–	50

†

†	58	–	13			by the instrumt
–			3	–	20	error of instrumt
	58	–	9	–	40
÷ 2.	29	–	4	–	50

Index Entries

astronomy; and calculations of Monticello’s longitude search
Buckingham County, Va.; TJ travels through search
Eppes, John Wayles (TJ’s son-in-law); TJ visits search
geography; and TJ’s calculations of latitude search
Jefferson, Thomas; Writings; Notes on the Latitude of Willis’s Mountain search
Monticello (TJ’s estate); latitude of search
Monticello (TJ’s estate); longitude of search
Poplar Forest (TJ’s Bedford Co. estate); TJ visits search
Randolph, Thomas Jefferson (TJ’s grandson; Jane Hollins Nicholas Randolph’s husband); and latitude of Willis’s Mountain search
Willis’s Mountain; TJ takes latitude of search

You Are Looking At

Source Project: Jefferson Papers
Title: Thomas Jefferson’s Notes on the Latitude of Willis’s Mountain, [ca. 19 December 1811]
Author: Jefferson, Thomas
Date: 19 December 1811

Reference

Cite as: “Thomas Jefferson’s Notes on the Latitude of Willis’s Mountain, [ca. 19 December 1811],” Founders Online, National Archives, https://founders.archives.gov/documents/Jefferson/03-04-02-0265. [Original source: The Papers of Thomas Jefferson, Retirement Series, vol. 4, 18 June 1811 to 30 April 1812, ed. J. Jefferson Looney. Princeton: Princeton University Press, 2007, pp. 344–346.]