Thomas Jefferson Papers

Thomas Jefferson to William Lambert, 29 December 1811

To William Lambert

Monticello Dec. 29. 11.


An absence of 6 weeks has prevented my sooner acknoleging your two favors of Nov. 14. & 22. which I found here on my return, the former with a letter from Bishop Madison. I am very thankful for your calculations on my observations of the late Solar eclipse. I have for some time past been rubbing off the rust of my mathematics contracted during 50. years engrossed by other pursuits, and have found in it a delight and a success beyond my expectations. I observed the eclipse of the sun with a view to calculate my longitude from it, but other occupations had prevented my undertaking it before my journey; and the calculations you have furnished me with shew it would have been more elaborate than I had expected, and that most probably I should have foundered by the way. one thing I do not understand, why you preferred using the external rather than the internal contacts. I presume the Bishop sent you the whole of the observations & the note on them which I shall subjoin to this. you will there percieve I had little confidence in the external contacts, but an entire one in the forming & breaking of the annulus. I have no telescope equal to observing the eclipses of Jupiter’s satellites, and as soon as I have fitted up a little box for my instruments, I shall amuse myself with the further ascertainment of my longitude by the lunar observations, which have the advantage of being repeated ad libitum, and of requiring less laborious calculations. Accept the assurances of my esteem & respect

Th: Jefferson

PoC (DLC); at foot of text: “Mr William Lambert”; endorsed by TJ; with PoC of Tr of enclosure on verso. Enclosure: extract from TJ to Henry A. S. Dearborn, 15 Nov. 1811.

Index Entries

  • astronomy; and calculations of Monticello’s longitude search
  • astronomy; and lunar calculations search
  • astronomy; and solar observations search
  • astronomy; Jupiter search
  • Jefferson, Thomas; Opinions on; mathematical study search
  • Jupiter (planet) search
  • Lambert, William; calculates Monticello’s longitude search
  • Lambert, William; letters to search
  • Madison, James, Bishop; and observations of solar eclipses search
  • Madison, James, Bishop; and W. Lambert’s astronomical calculations search
  • Monticello (TJ’s estate); longitude of search
  • Monticello (TJ’s estate); solar eclipse observed by TJ at search
  • moon; TJ’s observations of search
  • sun; and calculation of longitude search
  • sun; annular eclipse of1811observed search