Letter, from Johannes Hevelius to Henry Oldenburg, dated at Danzig (Gdansk) Praises the Royal Society; states that he will send his 'Cometographia' when it is published; states that a catalogue of fixed stars must be realised before any further work can take place; states that he is working on his 'Machina Coelestis' but that he needs the observations of King Ulug-Beg, which are found in a Persian manuscript in Oxford 4 January 1664