2134/33892 Kathryn Spalding Kathryn Spalding Alexander Veselov Alexander Veselov Conway river and Arnold sail Loughborough University 2018 untagged Mathematical Sciences not elsewhere classified 2018-07-13 13:59:57 Journal contribution https://repository.lboro.ac.uk/articles/journal_contribution/Conway_river_and_Arnold_sail/9384974 We establish a simple relation between two geometric constructions in number theory: the Conway river of a real indefinite binary quadratic form and the Arnold sail of the corresponding pair of lines.