Durandus was the author of several very learned rvorks. The most famous of them is his Speαdum Judiciale. This work is entitled in the juin ted copies, the earliest of which was published at home in folio in 1474, as Speculum Juris ; but all the MSS. have the title of Speadum Judiciale ; and Durandus himself, in his epistle dedicatory to Cardinal Ottobonus Fiesco, afterwards Pope Adrian V., describes it under this latter title. It is a practical treatise on civil and canon law, and it earned for its author, when young, the surname of the Father of Practice. Durandus is said to have completed it in 1271, at the age of thirty-four, and he revised it some time between 1287 and 1291. It has since his death acquired much celebrity as one of the best sources of the dogmatic history of law, and the canonists are accustomed to cite Durandus under the bye-name of “the Speculator.” The original work has been enriched by additions from the pen of John Andreae in 1346, and by further additions from the pen of Baldus. An alphabetic table of its contents (Inventorium) was drawn up by Cardinal Beranger in 1306, and the Speculum passed through thirty-eight editions between 1474 and 1678. The next important work of Durandus is his Repertorium Aureum or Breviarium, which is dedicated to Cardinal Matthaeus; Durandus himself in his preface designates this work by the name of Breviarium, but it is described by him in the Preface to the Specιdum by the title of Repertorium Aureum, under which title it is more generally known. It is supposed to have been composed by Durandus in the interval between the first completion and the revision of the Speculum. His Commentarius in Concilium Lugdunense is a work of much interest, as Durandus himself drew up the Decretals, which after his death were inserted in the Sextus. Durandus also wrote a commentary on the decretals of Pope Nicholas 111., which is only known to us from the epitaph on his tomb, as preserved by Sarti, and which enumerates all his chief writings, amongst which may be mentioned his Speculum Legatorum, inserted in the Specιdum Judiciale, his Rationale Divinorum Officiorum, which has passed through many editions, the earliest of which was printed at Mayence in 1459, and a copy of which is stated by the Abbé Pascal to ha·ve been sold for 2700 francs. A manuscript of his Pontificale Patrum, being a treatise on the duties of bishops, is preserved in the National Library of Paris. Durandus the Speculator is sometimes confounded with Durandus of Santo Porciano, bishop of Meaux, who died in 1332, and was the author of two treatises, De Jurisdictioni and De Legebus, and·withWilhelmus Durandus, his own nephew, who was the author of a work entitled De modo celebrandi Consilii, and who died in Cyprus in 1328.