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Thomas Jefferson’s Observations at Monticello Related to Calculation of Latitude, 11 October 1815–31 January 1816
Observations at Monticello Related to Calculation of Latitude
| date | Merid. Alt. by circle | same halved | merid. Alt. from horizon | difference | ⊕error of instrum. | ||||||||||||
| 1815. | ° ′ ″ | ° | ′ | ″ | ° | ′ | ″ | ° | ′ | ″ | ′ ″ | *satisfactory | |||||
| *Oct. | 11 | 90–18– 0 | 45– | 9 | – 0 | 45– | 26 | –0 | 0– | 17 | –0 | 6– 0 | † not satisfactory | ||||
| 13 | 88–29– 0 | 44– | 13 | –301 | 7–30 | ⊕ the line of collimation (or point of coincidence of the 2 images) which ought to be at the zero inscribed on the instrument is found to be really so many minutes below it. the measure of the vertical angle therefore commencing so much below it, the difference must be added if the upper graduation is used, or subtracted if the lower.2 |
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| 5– | |||||||||||||||||
| 18 | 85– 2–30 | *3–30 | |||||||||||||||
| *6 | |||||||||||||||||
| 19 | 84–22– 0 | 42– | 11 | – 0 | 42– | 34 | –0 | 0– | 23′ | –0 | *6 | ||||||
| * | 25 | 80– 6– 0 | 40– | 3 | – 0 | 40– | 23 | 0– | 20 | –0 | *6 | ||||||
| 1816. | |||||||||||||||||
| Jan. | 21 | 64– 0– 0 | 32– | 0 | – 0 | * | 1–30 | ||||||||||
| 29 | *67–58– 0 | 2–30 | |||||||||||||||
| 30 | B. | 68–28–30 | 4– | ||||||||||||||
| p | 68–26 | 3–30 | |||||||||||||||
| 31 | B | 68–56 | 3–30 | ||||||||||||||
| p | 68–25 | 4 | |||||||||||||||
MS (MHi); filed with TJ’s Weather Memorandum Book, 1802–16; written entirely in TJ’s hand on one side of a single sheet.
1. Thus in manuscript, but the correct figure is 44°–14′–30″.
2. Above this paragraph TJ canceled “⊕ the error to be subtracted where the count is on the lower graduan [i.e., graduation]; but to be added if on the upper.”
Index Entries
- astronomy; and calculations of Monticello’s latitude search
- Borda’s circle (surveying instrument) search
- Jefferson, Thomas; Writings; Observations at Monticello Related to Calculation of Latitude search
- latitude; calculations for Monticello search
- Monticello (TJ’s estate); latitude of search
- sun; and calculation of latitude search
- surveying; and J. C. Borda’s circle search