Letter not found: from Ernst Frederick Gayer (Guyer), c.24 April 1793. Thomas Jefferson wrote Gayer on 26 April: “I have duly received your letter of the 24th inst. inclosing a Memorial to the President on the subject of an instrument and table of your invention for ascertaining the longitude at sea, and desiring that the patent-board might appoint a time for examining into the same” and that the president was not “authorized to refer applications of this kind to any persons whatsoever” (Jefferson Papers, description begins Julian P. Boyd et al., eds. The Papers of Thomas Jefferson. 41 vols. to date. Princeton, N.J., 1950–. description ends 25:589–90).