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Thomas Jefferson’s Calculations of Latitude of Willis’s Mountain, 8-9 December 1816

Calculations of Latitude of Willis’s Mountain

Willis’s mountain. Long. W. from Greenwich. 78°–49′–31″

observations with Borda’s circle.

			Dec. 8. 1816		Dec. 9. 1816.
					° ′ ″
1816. Dec. 8.	½ observed alt. ⊙		29–49–30		29–44–30
−	error of instrumt		1–11	½	1–11	½

	true observd alt.		29–48–18	½	29–43–18	½
−	refractn + parallax		1–30		1–30
	true Altitude of ⊙		29–46–48		29–41–48
	decln Greenwich	22–45–51					22–51–51
	more for 79° W.	1–15	22–47– 6		22–53– 6		1–15
	true height of Æquator		52–33–54		52–34–54
			90–		90
	Zenith dist. = lat.		37–26– 6		37–25– 6

note the observn of Dec. 9. was compleatly perfect & satisfactory.

MS (MHi); filed with TJ’s Weather Memorandum Book, 1802–16; written entirely in TJ’s hand on verso of his Calculations of Latitude of Poplar Forest, 8 Nov.–3 Dec. 1816.

On a separate, narrow sheet, TJ recorded his key finding on these days:

“observns with Borda W’s. Mount.

1816.			°	′
Dec.	8.	mer. alt. ⊙	59–	39/	29
	9		59–	29½

note this last was a most perfect observn. the 1st not perfect” ( in ; filed with TJ’s Weather Memorandum Book, 1802–16; entirely in TJ’s hand, with his related calculations of instrument error for his Borda’s circle, headed “1816. Nov. Dec. error of Borda,” on verso).

Index Entries

astronomy; and calculations of Willis’s Mountain’s latitude search
Borda, Jean Charles de; and surveying instruments search
Borda’s circle (surveying instrument) search
geography; and TJ’s calculations of latitude search
Greenwich Observatory, England; and prime meridian search
Jefferson, Thomas; Writings; Calculations of Latitude of Willis’s Mountain search
latitude; calculations for Willis’s Mountain search
sun; and calculation of latitude search
surveying; and J. C. Borda’s circle search
Willis’s Mountain; TJ takes latitude of search

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Source Project: Jefferson Papers
Title: Thomas Jefferson’s Calculations of Latitude of Willis’s Mountain, 8-9 December 1816
Author: Jefferson, Thomas
Date: 8 December 1816

Reference

Cite as: “Thomas Jefferson’s Calculations of Latitude of Willis’s Mountain, 8-9 December 1816,” Founders Online, National Archives, https://founders.archives.gov/documents/Jefferson/03-10-02-0434. [Original source: The Papers of Thomas Jefferson, Retirement Series, vol. 10, May 1816 to 18 January 1817, ed. J. Jefferson Looney. Princeton: Princeton University Press, 2013, pp. 571–572.]