Unpublished manuscript, 'Description of a quadrant for measuring horizontal angles by reflection' by W [William] Barnes Barnes describes the construction of his quadrant used to measure horizontal angles. The quadrant consists of a frame, an arch, a nonius, an index glass, an object glass, and a light vane. Peter Mark Roget's initials appear next to the date received. Below this, an ink inscription reads 'Not to be read' and below this, 'Not fit for the R. S. H.K. [Henry Kater]'. Underneath this is a copy of Kater's comment, with John George Children's initials. Subject: Scientific Instruments Received by the Royal Society on 7 August 1830. [1830]