These books have a twofold origin. Some are laboratory notebooks in the usual sense, documenting experimental work with dates and descriptions, and sometimes kept partly by research assistants and collaborators as well as by Appleton himself. Others are more diverse, and belong to the category of 'little black books'. Appleton's lifelong habit of keeping small notebooks in his pockets was well known and commented on by his biographers, who often quote from them. The description 'little black books' is clearly no more than a generic term, since very few are black and some are quite large. Nevertheless they have many features in common; few are dated, and Appleton seems to have kept several of them in play at the same time so that each book might remain in sporadic use for years, entries being made at the front, back, or on odd blank pages in the middle. Conversely, certain books are hardly used at all. The content is heterogeneous and includes notes for experiments to be performed, theories to be tested or papers to be written, diagrams, calculations and 'thinking aloud', notes on the literature, of lectures or discussions at conferences, of points to be raised at meetings, quotations, anecdotes, epigrams or longer paragraphs for inclusion in Appleton's speeches or writings - not all of them on scientific subjects. To a small extent, the material is similar to the diaries in Section A, but the notebooks in Section B differ in containing only Appleton's ideas on scientific or general topics with no details of engagements or chronology. Dated material, or that to which a date can be tentatively assigned on internal evidence, is presented as a sequence. Undated material is placed at the end of the sequence (Coll-37/B.48-B.57). All the material is in Appleton's hand unless otherwise stated. Further research material in the form of loose notes and narratives, graphs and data, and exchanges of correspondence, is in Section C. Additional notebooks can be found at Coll-37/C.310, C.311 (Tromsö expedition), C.256 (radar) C.384-C.388 (valves), D.67, D.68 (lecture material), H.1. Attention is drawn to B.58 - B.60, which comprise two bound volumes and one folder of press-cuttings recording developments in 'wireless', radio and television. Appleton began the first of these (B. 58) during the First World War and continued somewhat less methodically until about 1939.