'Liber Supputationum' ('A book of calculations'), 113 folios, including work relating to the comet of 1680-1681 (1v-25v); optics, with a diagram marked 'Lectura 2a' (between 32v and 43r); Jupiter's satellites (passim after 46r) and the equation of light, with Römer's table (98v); lunar and solar eclipses (50r-54v, 65r-66r); the weight of metals (55v-56r); Saturn and Jupiter (passim after 85r); notes on 'Dr Goads Weather May 1682' (108rv); and 'Monsieur Picarts table of Refractions' (110rv). The volume was begun on 12 January 1681, and has dates up to 1 January 1684. The writing throughout is in Flamsteed's hand. There is an incomplete list of contents at the end (110rv).