All this material was received crammed into Milne's original folder inscribed 'Notes on Statistical Mechanics'. It consists mainly of notes for courses of lectures at various dates, probably all at Oxford; MS. Eng. misc. c. 426/C.28 is early (c.1928), much of MS. Eng. misc. c. 426/C.29 et seq are later (c.1937). There are also analytical notes on earlier theories, presented here alphabetically for convenience, with Milne's comments or re-workings, and some longer narratives for lectures or publications.