In some cases the oak covers of manuscripts were not hidden by leather, but were decorated by elaborate paintings. A very interesting series of folio account-books of the Cathedral of Siena, now preserved in the _Opera del Duomo_, are specially remarkable for their pictured bindings. These manuscripts date from about 1380 to 1410, one volume being devoted to the expenses and records of each year. On one of the covers of each is a large painting on the oak, frequently of a view of some part of Siena or of the interior of the Cathedral. Very interesting evidence with regard to the old fittings of the high altar, with Duccio di Buoninsegna's great retable, and the original position of the magnificent pulpit are given by some of these pictured covers. One volume of this Sienese series is now in the South Kensington Museum. _Stamped leather._ In the fourteenth century bindings of books began to be decorated by stamping patterns with dies or punches on the vellum or pigskin covering of the oak board; a method of decoration which was greatly elaborated and developed in the sixteenth century, especially by the German and Dutch bookbinders. The earlier stamped designs were of a much simpler character, usually consisting of powderings all over the surface of the cover, with small flowers or animals, such as lions, eagles, swans and dragons of heraldic character. In many cases these punches, or at least their designs, continued in use for a long time, and so one occasionally meets with a fifteenth century book, the binding of which is decorated with stamps of fourteenth or even thirteenth century style. _Stamped bindings._ The later class of stamped bindings, belonging rather to printed books than to manuscripts, is often very beautiful and decorative in character, the whole surface of the cover being completely embossed in relief by the skilful application of a great number of punches used in various combinations, so as to form one large and perfectly united design. In these later times, from about the middle of the sixteenth century the tendency was to cut larger designs on one punch or die; and the leather or parchment was softened by boiling so that a large surface could be embossed at one operation. This process was much aided by the invention of the screw-press, which enabled the workman to apply a steady and long-continued pressure. But in the older stamped bindings, as a rule, small punches were used, and the force was simply applied by the blow of a hammer[297]. _English bindings._