MICHAEL, a learned Maronite, was born at Tripoli in 1710. He studied at Rome, where he afterwards for ten years taught Arabic, Syriac, and Chaldee, and gave lectures in philosophy and theology. In 1748 he went to Spain, and was employed in the royal library at Madrid. He was successively named a member of the royal academy of history, interpreter of oriental languages to the king, and joint librarian of the Escorial, with a royal pension of 200 piastres. In 1763 he became principal librarian, a situation which he appears to have held till his death in 1791.

Casiri published a work entitled Bibliotheca Arabico-Hispana Escurialensis, 2 vols. fol., Madrid, 1760–1770. It is a catalogue of above 1800 Arabic MSS. contained in the library of which he was keeper. They are arranged under the heads of Grammar, Rhetoric, Poetry, Philology, and Miscellanies, Lexicons, Philosophy, Politics, Medicine, Natural History, Jurisprudence, Theology, Geography, and History. The last two classes, with a copious index, occupy the whole of the second volume. A full view of its contents, with some political comments, is given in the first appendix to Harris's Philological Inquiries, and in the second appendix to Barrington's Literary History of the Middle Ages.