Used to describe both binary systems and optical doubles, the term 'double star' has been familiar to astronomers since the seventeenth century. This book, first published in 1879, outlines the history of their study, and describes the methods and equipment needed in order to observe the fascinating phenomenon. Written for non-specialists by Fellows of the Royal Society Edward Crossley (1841-1904), Joseph Gledhill (1837-1906) and James M. Wilson (1836-1931),...