Thomas Jefferson Papers

Thomas Jefferson to Henry A. S. Dearborn, 15 November 1811

To Henry A. S. Dearborn

Monticello Nov. 15. 11.


Your favor of Oct. 14. was duly recieved, and with it mr Bowditch’s observations on the comet, for which I pray you to accept my thanks, and to be so good as to present them to mr Bowditch also. I am much pleased to find that we have so able a person engaged in observing the path of this great phaenomenon; and hope that from his observations & those of others of our philosophical citizens on it’s orbit we shall have ascertained, on this side of the Atlantic, whether it be one of those which have heretofore visited us. on the other side of the water they have great advantages in their well established Observatories, the magnificent instruments provided for them, and the leisure & information of their scientific men. the acquirements of mr Bowditch in solitude & unaided by these advantages do him great honor:

With respect to the eclipse of Sep. 17. I know of no observations made in this state but my own, altho’ I have no doubt that others have observed it. I used myself an Equatorial telescope, & was aided by a friend, who happened to be with me, and observed thro’ an achromatic telescope of Dollond’s. two others attended the timepieces.1 I had a perfect observation of the passage of the sun over the meridian, and the eclipse commencing but a few minutes after, left little room for error in our time. this little was corrected by the known rate of going of the clock. but we as good as lost the first appulse by a want of sufficiently early attention to be at our places, & composed. I have no confidence therefore, by several seconds, in the time noted. the last osculation of the two luminaries was better observed.2 yet even there was a certain term of uncertainty as to the precise moment at which the indenture on the limb of the sun entirely3 evanished. it is therefore the forming of the annulus, & it’s breaking, which alone possess my entire & compleat confidence. I am certain there was not an error of an instant of time in the observation of either of them. their result therefore should not be suffered to be affected by either of the others. the four observations were as follows.4

The 1st appulse 0–13–54 ————————— }
annulus formed 1–53– 0 } central time of central time of the
annulus broken 1–59–25 annulus 1 H–56′–12½″ two5 contacts 1 H–51′–28″
last osculation 3–29– 26 —————————

Latitude7 of Monticello 38°–8′

I have thus given you, Sir, my observations, with a candid statement of their imperfections. if they can be of any use to mr Bowditch, it will be more than was in view when they were made; and should I hear of any other observations made in this state, I shall not fail to procure & send him a copy of them. be so good as to present me affectionately to your much esteemed father, & to accept the tender of my respect.

Th: Jefferson

RC (Mrs. Henry I. Bowditch, Jamaica Plain, Mass., 1946); addressed: “Mr H. A. S. Dearborn Boston”; franked; postmarked Milton, 18 Nov. 1811. PoC (DLC). PoC of 1st Tr (DLC: TJ Papers, 194:34537); undated extract in TJ’s hand enclosed in TJ to William Lambert, 29 Dec. 1811. 2d Tr (DLC: TJ Papers, ser. 7, Weather Record, 1776–1818); undated extract in TJ’s hand; at head of text: “Observation of the Annular eclipse of the ☉ Sep. 17. 1811. at Monticello.”

Nathaniel Bowditch made use of TJ’s observations in his article “On the Eclipse of the Sun of Sept. 17, 1811, with the longitudes of several places in this country,” Memoirs of the American Academy of Arts and Sciences 3 (1815): 255–304, esp. 268–9, 297, 299. See also TJ to Bowditch, 2 May 1815.

In 1805 TJ attached a twelve-inch telescope to his Universal equatorial Instrument, a sophisticated device manufactured by London instrument-maker Jesse Ramsden. It used clockwork settings to track celestial bodies across the sky. In 1793 TJ acquired his equatorial, for a time the only one in the United States (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 , 2:888, 1170; PTJ description begins Julian P. Boyd, Charles T. Cullen, John Catanzariti, Barbara B. Oberg, and others, eds., The Papers of Thomas Jefferson, 1950– , 31 vols. description ends , 24:287–9; Silvio A. Bedini, Thomas Jefferson: Statesman of Science [1990], 228–30). The friend and others who attended the observation of the annular solar eclipse at Monticello on 17 Sept. 1811 may have included President James Madison and his secretary Edward Coles (Madison, Papers description begins William T. Hutchinson, Robert A. Rutland, John C. A. Stagg, and others, eds., The Papers of James Madison, 1962– , 29 vols.: Congress. Ser., 17 vols.; Pres. Ser., 5 vols.; Sec. of State Ser., 7 vols description ends , Pres. Ser., 3:460; TJ to Joseph Dougherty, 19 Sept. 1811). TJ purchased his achromatic telescope from the London opticians Peter & John Dollond in March 1786 (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 , 1:614). An appulse is the coming into conjunction of two heavenly bodies (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 ).

1Both Trs begin here.

2Both Trs: “in the time noted for the 1st external contact. the last was better observed.”

3Both Trs: “exactly.”

4Preceding six words omitted from both Trs. The PoC of 1st Tr gives the table of observations above the explanatory paragraph.

5PoC of 1st Tr here adds “external.”

62d Tr provides only the first column of the table, but adds to the right of it: “by the calculations of Wm Lambert, a calculator of the first order in point of accuracy the outer contacts give the Long. of Monto 78°–35′–10.95″ the inner (West from Greenwich) 78–50–18.877 which last is to be considered as the true longitude” (see Lambert to TJ, 14 Nov. 1811, 8 Jan. 1812). 2d Tr concludes with TJ’s later notation that “Mr Bowditch of Salem makes the Longitude of Monto from the same elements 78–47–36.”

7PoC of 1st Tr ends immediately before this word.

Index Entries

  • astronomy; and calculations of Monticello’s longitude search
  • astronomy; and solar observations search
  • astronomy; astronomical instruments search
  • Bowditch, Nathaniel; and solar eclipse search
  • Bowditch, Nathaniel; The Comet: Elements of the Orbit of the Comet, now visible search
  • clocks; and solar eclipse search
  • Coles, Edward; observes solar eclipse search
  • Dearborn, Henry; TJ sends greetings to search
  • Dearborn, Henry Alexander Scammell; and astronomy search
  • Dearborn, Henry Alexander Scammell; letters to search
  • Dollond, Peter & John (London firm); TJ purchases telescope from search
  • equatorial (astronomical instrument); owned by TJ search
  • geography; and TJ’s calculations of latitude search
  • Lambert, William; calculates Monticello’s longitude search
  • Madison, James; and solar eclipse search
  • Monticello (TJ’s estate); latitude of search
  • Monticello (TJ’s estate); longitude of search
  • Monticello (TJ’s estate); solar eclipse observed by TJ at search
  • Ramsden, Jesse; equatorial of search
  • scientific instruments; equatorials search
  • scientific instruments; telescopes search
  • sun; annular eclipse of1811observed search
  • telescopes; equatorial search
  • telescopes; used to observe solar eclipse search
  • The Comet: Elements of the Orbit of the Comet, now visible (Bowditch) search