One method, called “web glazing,” is to pass the paper between a number of rolls, alternately of polished iron and very highly compressed paper or cotton. The construction of such a calender will be understood by reference to Figs. 58 (end elevation) and 59 (front elevation). The reel of paper, as taken from the machine, is shown at A (Fig. 58), its course over the rolls being indicated by arrows. After passing over the bottom roll, it is wound off on a wooden or hollow iron cylinder B (Fig. 58), driven by the toothed wheel shown by the dotted line C, on the same shaft as the wheel D, which is driven by E, keyed upon the bottom roll. The whole machinery is driven by the large toothed wheel F (Figs. 58 and 59), which is itself driven by the small wheel G on the main shaft H. The paper rolls are marked P, and the iron rolls I. It will be seen that there are two paper rolls in the middle, for the purpose of, as it were, reversing the paper, and so making both sides alike. Pressure is applied to the rolls by means of the screws K, and by the weight L (Fig. 58) acting on the compound lever M. The brake, which consists of a strap of leather, pressing, by means of the weight and lever N, on the circumference of the wheel O, connected by toothed wheels with the cylinder A on which the paper is wound, is used for the purpose of preventing the paper from leaving {168} the cylinder too rapidly. But for this appliance, the paper would be apt to crease. The paper rolls have an inner core of iron, the paper only extending to a depth of about 5 in. The iron rolls are hollow, and are connected with steam-pipes, by which they can be heated. {169} [Illustration: FIG. 59.] Another method, known as “friction-glazing,” employed for giving a very high finish to paper, generally on one side only, is to pass it between a large paper roll and a smaller iron one, the latter revolving at a much greater speed than the {170} former. By this means a very smooth surface can be obtained. It is sometimes assisted by rubbing a small quantity of bees’-wax on the small iron roll. The above-mentioned methods apply to the glazing of paper in the web. Paper cut into sheets may also be treated in the same way. Various modifications of these calenders have been devised; they do not, however, involve the application of any special principle. Plate-glazing, a method that is adapted to hand-made and the better qualities of paper, consists in applying heavy pressure to sheets placed between polished plates of copper or zinc. The metallic plates and the sheets of paper are made into bundles, and the whole is passed between two strong rolls, heavy pressure being communicated to them by means of screws or levers and weights applied to the ends of the upper roll. [Illustration: FIG. 60.]