The mathematical treatises known as Ta?r?r al-mutawassi??t, “Revision of the Middle books”, are a collection of Greek and Arabic treatises which were re-edited by Na??r al-D?n al-??s?. This paper explores the nature of the editorial work ??s? did, showing that it is not a simple rendering of the original text but that it involves major revisions and in fact original additions. For the first time, a collated version of ??s?’s revision on the treatise on the measurement of the circle (by Archimedes) is provided. A translation of the Arabic text is put side by side with a rendition of the treatise as it was circulated before ??s?’s time. An in-depth analysis of the text elucidates the nature of ??s?’s contributions to the text. This article also provides modest corrections to earlier studies by W. R. Knorr and P. Luckey.
