This book, first published by Cambridge University Press in 1955, investigates the origins of The Equatorie of the Planetis, a fourteenth-century manuscript in the library of Peterhouse, Cambridge. Dr Price, a historian of science, examines the idea that it was composed and written by Geoffrey Chaucer. The chapters discuss the problems of ascription, bibliography and palaeography as well as giving an account of the theories and history of medieval astronomy and the Equatorie instrument. This edition reproduces, translates and describes the complete manuscript and uses various photographic techniques to examine erased words and analyse Chaucer's signature on the document. There are facsimiles of pages from the astronomical tables together with an analysis of their contents, and a selection of extracts from other unpublished Middle English astronomical texts are included in the appendices. A glossary is provided by R. M. Wilson.