Recent travels. Dangers and difficulties of triangulation survey. Observations of variable brightness of Eta Argus. [Letter continues 29 December] Returned from 'Pequet Brig,' leaving C. P. Smyth with theodolite. Events in colony. Sending observations of Encke's Comet for R.A.S. Observations of 'great comet of March.' News of Nathaniel Wallich and family. Sends 'plan of the Herschel obelisk drawn by Smyth.' Details of obelisk. Progress on observations of 'Parallax stars.' Organized system to prevent mistakes in calculating and copying meridian work.