Addai Scher (1867-1915), who was killed during the catastrophes and tumults of 1915, is well known for his work with manuscript collections he had access to in the Middle East. While unfortunately much of this manuscript material was subsequently destroyed or lost, his descriptions retain their value for scholars working in Syriac and Christian Arabic literature. The present work covers the Syriac (and some Arabic) manuscripts then located at the Chaldean Patriarchal Library in Mosul. The catalog includes Scripture and commentaries, theology, philosophy, liturgical texts, canon law, poems, homilies, hymns, hagiography, ascetic works, grammar and lexicography, letters, and history: in short, a very broad and rich collection. An index of authors and anonymous works concludes this immensely valuable reference work.