Green notebook labelled on cover 'B' and on first page 'Book B. 1921-22 Catalogue of alpha-ray photographs November 1921. P.M.S Blackett, Magdalene College. If found please return to above address'. The first few pages of the notebook 9pages are not numbered) contain record of 28 photographs. This is followed by a 'Catalogue of interesting tracks, etc.' (6pp) and 'notes on general appearance of films (4pp). The notebook then contains a 139pp series of detailed analyses of photographs. This is a catalogue of Blackett's first research at the Cavendish under Rutherford. See Bernard Lovell, P.M.S. Blackett: A Biographical Memoir, Royal Society: 1976, pp6-7, which describes Blackett's modifications to the apparatus and two series of experiments. The record of experiments with a mixture of 75% argon + 15% notrogen ends on p75. On pp 9-10 there are calculations in Rutherford's hand. 1921-1922