Calculations of Latitudes of the Sharp Peak of Otter and Natural Bridge
|1815. Sep. 18. Sharp peak of Otter||°||′||″||1815. Sep. 20. Natural bridge.||°||′||″|
|Observed altitude of ⊙.||109||–||21||–||0||107||–||29||–||0|
|− error of instrument||1||–||30||1||–||30|
|true observed altitude||54||–||39||–||45||53||–||43||–||45|
|− refractn 41″ + parallax 4″||37||− 42″ + 4″1||38|
|true altitude of ⊙’s center||54||–||39||–||8||53||–||43||–||7|
|− ⊙’s decln Greenwich||2–7–17||1°–20′– 42″|
|for 79°–45′–57.″ W||5– 8||2||–||12||–||25||5 – 9||1||–||25||–||51|
|true height of Æq.2 at Peak||52||–||26||–||43||52||–||17||–||16|
|Zenith distance of Æq. at Peak||37||–||33||–||173||37||–||42||–||44|
|1815. Nov. 10. Sharp peak of Otter||°||′||″|
|− error of instrument||1||–||30|
|true observed altitude||35||–||33||–||15|
|− refractn 1′–19″ + parallax 7″=||−||1||–||12|
|true Alt. of ⊙’s center||35||–||32||–||3|
|⊙’s decln Greenwich||17°–0′– 1″|
|for 79°–45′–57.″ W. +||3 –33||17||–||3||–||33|
|height of Æq. at Peak||52||–||35||–||36|
|Zenith dist. or Lat.||37||–||24||–||24|
|observn of Sep. 18.||37||–||33||–||17|
|mean of 2. observations||37||–||28||–||50|
MS (MHi); filed with TJ’s Weather Memorandum Book, 1802–16; on verso of TJ’s Calculations of Latitude of Poplar Forest, 6 Aug.–10 Dec. 1815 (printed at the latter date); entirely in TJ’s hand. Dft (CSmH: JF); on verso of TJ’s Notes on Distances between Poplar Forest and Natural Bridge, [ca. 17–21 Sept. 1815], and TJ’s MS pocket notes for his 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 entries covering 17–21 Sept. 1815; entirely in TJ’s hand; lacking calculations for 10 Nov. and textual explanation of calculations for 18 and 20 Sept.
TJ also created, but never used, a sheet with four additional blank versions of the chart employed here, two each on recto and verso (MS in MHi; filed with TJ’s Weather Memorandum Book, 1802–16; entirely in TJ’s hand; dated Sept. 1815).
TJ confirmed elsewhere that he observed the latitudes of the Sharp Peak of Otter and of Natural Bridge as 37°–33′–17″ and 37°–42′–44″ on sep. 18 and sep. 20, respectively (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 , 2:1313, 1314). He also noted in a handwritten revision to the query on mountains in his Notes on the State of Virginia, composed sometime after November 1815, that “Two observns with an excellent pocket sextant gave a mean of 37°–28′–50″ for the Lat. of the sharp Peak of Otter” (Jefferson, Notes on the State of Virginia [London, 1787; Sowerby, description begins E. Millicent Sowerby, comp., Catalogue of the Library of Thomas Jefferson, 1952–59, 5 vols. description ends no. 4167; Poor, Jefferson’s Library description begins Nathaniel P. Poor, Catalogue. President Jefferson’s Library, 1829 description ends , 7 (no. 365); TJ’s copy with revisions in ViU, including this one tipped in between pp. 28 and 29]).
1. Equation not in Dft.
2. Abbreviation for “Equator,” here and below.
3. In Dft TJ canceled a preliminary version of his 18 Sept. calculation and replaced it with one that corrected a subtraction error in the first step.
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