We must not forget to mention, among the most beautiful bindings of the eleventh and twelfth centuries, the coverings of books in enamelled copper (Fig. 380). The Museum of Cluny possesses two plates of incrusted enamel of Limoges, which must have belonged to one of these bindings: the first has for its subject the “Adoration of the Magi;” the other [Illustration: IVORY DIPTYCH OF THE LOWER EMPIRE. Serving as a Book Cover, “l’Office des fous.”. (In the Library of Sens)] represents the monk Etienne de Muret, founder of the order of Grandmont (in the twelfth century), conversing with St. Nicholas. The Cathedral of Milan contains in its treasury the covering of a book still more ancient and much richer, about fourteen inches long by twelve inches wide, and profusely covered with incrusted enamel, mounted and ornamented with polished, but uncut, precious stones of various colours. [Illustration: Fig. 379.--Library of the University of Leyden, in which all the Books were chained, even in the Seventeenth Century.] But all these were only the work of enamellers, goldsmiths, illuminators, and clasp-makers. The binders, or bookbinders properly so called, fastened together the leaves of books, and placed them between two boards, which they then covered with leather, skin, stuff, or parchment; they added to these coverings sometimes leathern straps, sometimes metal clasps, sometimes hooks, to keep the volume firmly closed, and almost always nails, whose round and projecting heads preserved the flat surface of the binding from being rubbed. In the year 1299, when the tax was imposed upon the inhabitants of Paris for the exigencies of the king, it was ascertained that the number of bookbinders then actually in the town amounted only to seventeen, who, as well as the scribes and booksellers, were directly dependent on the [Illustration: Fig. 380.--Large Painted Initial Letter in a Manuscript in the Royal Library, Brussels, showing the arrangement of the Binding, in enamelled Metal, of a book of the Gospels. (Ninth or Tenth Century.)] University, the authorities of which placed them under the surveillance of four sworn bookbinders, who were considered the _agents_ of the University. We must except, however, from this jurisdiction the acknowledged bookbinder to the “Chambre des Comptes,” who, before he could be appointed to this office, had to make an affirmation _that he could neither read nor write_.