Thomas Jefferson’s Calculations of Latitude of Poplar Forest, 8 November–3 December 1816
Calculations of Latitude of Poplar Forest
| Nov. 8. | ° ′ ″ | Nov. 9. | ° ′ ″ | Nov. 12. | ° ′ ″ | Nov. 13. | ° ′ ″ | Nov. 15.1 | ° ′ ″ | |||||||
| ½ | observed altitude of ☉ | 36– 1–30 | 35–44– 0 | 34–55–30 | 34–37–452 | 34– 0– 6 | ||||||||||
| − ½ | error of instrument | 1–11½ | 1–11½3 | 1–11½ | 1–11½ | 1–11½ | ||||||||||
| true observed altitude | 36– 0–18½ | 35–42–48½ | 34–54–18½ | 34–36–33½ | 33–58–54½ | |||||||||||
| − refraction + parallax | 1–10½ | 1–11½ | 1–14½ | 1–15½ | 1–16½ | |||||||||||
| true altitude of ☉’s center | 35–59– 8 | 35–41–37 | 34–53– 4 | 34–35–18 | 33–57–38 | |||||||||||
| ☉’s declinn Greenwich | 16–38–30 | 16–55–47 | 17–45–52 | 18– 1–57 | 18–33–11 | |||||||||||
| + at Poplar Forest 79°–46′ | 3–42 | 16–42–12 | 4– 5 | 16–59–52 | 3–26 | 17–49–18 | 3–22 | 18– 5–19 | 3–13 | 18–36–24 | ||||||
| true height of Æq. at P.F. | 52–41–20 | 52–41–29 | 52–42–22 | 52–40–37 | 52–34– 2 | |||||||||||
| 90– | 90 | 90 | 90 | 90– | ||||||||||||
| zen. dist. Æq. = Lat. of P.F. | 37–18–40 | 37–18–31 | 37–17–38 | 37–19–23 | 37–25–58 | |||||||||||
| Nov. 214 | ° ′ ″ | Nov 22 | ° ′ ″ | Nov. 23 | ° ′ ″ | Dec. 3 | ° ′ ″ | ° ′ ″ | ||||||||
| ½ | observed altitude of ☉ | 32–39–30 | 32–30–30 | 32–15–45 | 30–35–155 | Dec. 3.6 | 37–16–26 | |||||||||
| ½ | error of instrument | 1–11½ | 1–11½ | 1–11½ | 1–11½ | Nov. 22. | 37–17–33 | |||||||||
| true observed Alt. | 32–38–18½ | 32–29–18½ | 32–14–33 | 30–34– 3½ | 12. | 37–17–38 | ||||||||||
| − refraction + parallax | 1–21½ | 1–22¼ | 1–22¼ | 1–28 | 9. | 37–18–31 | ||||||||||
| true alt. of ☉’s center | 32–36–57 | 32–27–56¼ | 32–13–11 | 30–32–35 | 8. | 37–18–40 | ||||||||||
| ☉’s declinn Greenwich7 | 19–58–48 | 20–11–50 | 20–24–29 | 22– 9–15 | 13. | 37–19–23 | ||||||||||
| +8 at Poplar Forest | 2–46 | 20– 1–34 | 2–41 | 20–14–31 | 2–36 | 20–27– 5 | 1–44 | 22–10–59 | 23. | 37–19–44 | ||||||
| true height of Æq. at P.F. | 52–38–31 | 52–42–27 | 52–40–16 | 52–43–34 | 21. | 37–21–29 | ||||||||||
| 90 | 90 | 90 | 90 | 298–29–24 | ||||||||||||
| Zen. dist. of Æq. = Lat. P.F. | 37–21–29 | 37–17–33 | 37–19–44 | 37–16–26 | ⅛ | 37–18–40 | ||||||||||
MS (MHi); filed with TJ’s Weather Memorandum Book, 1802–16; written entirely in TJ’s hand on one side of a sheet, with his Calculations of Latitude of Willis’s Mountain, 8–9 Dec. 1816, on verso; partially dated.
Æq.: “equator.”
1. Entry for this date canceled by TJ with a diagonal line.
2. Number inserted by TJ in place of “69–15–30.”
3. Manuscript: “1–11–11½.”
4. Number inserted by TJ in place of “20?”
5. Number inserted by TJ in place of “61–10–30.”
6. At head of this column TJ canceled “Dec. 4” and readings of 30°–51′–45″ for half the observed altitude and 1′–11½″ for half the instrument error. In addition, TJ entered another reading for half of the observed altitude along the verso’s lower lefthand margin: “Dec. 5. 30°–15′–45″.”
7. Manuscript: “Greewich.”
8. Editorially corrected from minus sign in manuscript.
Index Entries
- astronomy; and calculations of Poplar Forest’s latitude search
- geography; and TJ’s calculations of latitude search
- Greenwich Observatory, England; and prime meridian search
- Jefferson, Thomas; Writings; Calculations of Latitude of Poplar Forest search
- latitude; calculations for Poplar Forest search
- Poplar Forest (TJ’s Bedford Co. estate); latitude of search
- sun; and calculation of latitude search