Title: The Book of Remedies from Deficiencies in Setting Up Marble Sundials

Description

This work is a treatise for timekeepers (singular muwaqqit), and discusses the telling of time from such astronomical observations as the sun’s angle of inclination (mayl), altitude (irtifā‛), as well as the direction (samt) and length of cast shadows (z#ill). In 14 chapters, the author goes through methods for the computation of these factors, determination of the direction of prayer (qibla), and time of the day. He observes that using instruments (ālāt), such as markings on the ruler (mist)ara) and the compass (bargār, from the Persian pargār), and geometric methods are straightforward, but inaccurate nevertheless. Therefore, he sets out to explain the arithmetical (h#isāb) aspects of astronomical measurements. His work contains numerous geometric diagrams and is rich with tables based on those prepared by Abu al-‛Abbās Ah#mad b. Muh#ammad b. Kathīr al-Farghānī, also known in the history of astronomy as Alfraganus. The latter had visited Egypt in 861 (247 A.H.) to supervise the construction of the Nilometer. The scribe’s name is Ramad#ān b. S#ālih# b. ‛Umar b. Ḥijāzī b. ‛Umar al-Ḥāfiz# al-Muqrī, known as S#afit)ī.