Correspondence between T. Henderson, G.B. Airy and T. Maclear, comprising a letter from Henderson aboard H.M.S. 'Melville', 25 January 1832; a letter from Henderson concerning tables of corrections for the microscopes on the mural circle, 27 September 1833; a list of observations with the transit circle, 10 April 1832 - 24 May 1833, and the mural circle, 16 May 1832 - 24 May 1833, with a list of corrections to mural circle microscope readings, dated 27 September 1833; a memorandum by Henderson, dated 3 October 1833, on the observatory set up by Mason and Dixon to observe the 1761 Transit of Venus; and a letter from Henderson concerning Encke's Comet, 17 October 1838, including a cutting from 'The Times' containing a letter from James South stating that he did not find the Comet. Folios 120-122 are a paper by Henderson on the parallax of Sirius.