Various sequences of notes and narratives, undated, the majority probably from the 1920s when Milne was working on atmospheric problems in astrophysics. The material was mainly intended for lectures and class problems but also in part for Milne's article 'Thermodynamics of the Stars' published as part of the Handbuch der Astrophysik (Berlin, 1930), or for other published work. Milne continued to lecture and publish on stellar thermodynamics throughout the 1930s, revising and updating his material accordingly. All the sequences, and the titles or opening phrases below, are Milne's.