This large work, originally published in successive volumes, contains a treatise on the Patriarchs of the Church of the East, taken from the Liber turris, due in its early form to Mari bin Sulayman (12th cent.) but later edited by 'Amr bin Matta and Saliba bin Yohannan (14th cent.). The Arabic text is given together with a Latin translation. In addition, a number of helpful indices are supplied: an Arabic index of people and places, an index of foreign (loan) words (mostly from Syriac) with Latin definitions, and variant readings; for the Latin translation, there is an index of the Patriarchs and also tables on computing the date of easter for the years covered in the work. This important volume is essential reading for students and scholars of the history of the Church of the East.