Thomas Jefferson Papers

Robert Patterson to Thomas Jefferson, 24 October 1815

From Robert Patterson

Philadelphia 24h Octr 1815


I have been favoured with your letter of the 13th & shall immediately take measures to send on your Time-piece as you have directed.

I have had, for some years an artificial horizon, which, by means of a reflecting sextant, answers the purpose of measuring all altitudes of the sun, or any other visible object, from 0 to 90° as well as all depressions not exceeding 50° with great ease & accuracy; & shall, Sir, have one made for you, on the same principles, to be sent on with the Time-piece; tho this may possibly occasion a delay of one or two weeks.

Mr Hassler has just arrived here from England, with a complete apparatus of mathematical & astronomical instruments, for the use of the Government; in taking a survey of the coast &c The pendulum of his astronomical clocks is on the same construction with that used in the Observatory of Greenwich. I expect to obtain from him one of the same kind for your Time-piece.

I am, Sir, with the greatest respect & esteem, your most obedt Servt

Rt Patterson

RC (DLC); endorsed by TJ as received 15 Dec. 1815 and so recorded in SJL. RC (DLC); address cover only; with PoC of TJ to Jean David, 25 Dec. 1815, on verso; addressed: “Thomas Jefferson Monticello Va”; franked; postmarked Philadelphia, 24 Oct. Dft (PPAmP: Thomas Jefferson Papers); on verso of remnant of address leaf of TJ to Patterson, 13 Oct. 1815; right half of page torn away, resulting in substantial loss of text; in heavily abbreviated form; with concluding section apparently differing significantly from RC but unrecoverable due to damage and illegibility.

Index Entries

  • artificial horizon; sent by R. Patterson search
  • clocks; TJ’s astronomical case clock search
  • Greenwich Observatory, England; pendulum at search
  • Hassler, Ferdinand Rudolph; and instruments for U.S. Coast Survey search
  • Patterson, Robert; and artificial horizon search
  • Patterson, Robert; and astronomical case clock search
  • Patterson, Robert; letters from search
  • pendulum; in clocks search
  • scientific instruments; artificial horizon search
  • scientific instruments; for U.S. Coast Survey search
  • scientific instruments; pendulums search
  • scientific instruments; sextants search
  • sextant; uses of search
  • surveying; U.S. Coast Survey search