In well-finished rooms the order is usually imagined as resting, not on the floor, but on pedestals, or rather on a continuous pedestal. This continuous pedestal, or "dado" as it is usually called, is represented by a plinth surmounted by mouldings, by an intermediate member often decorated with tablets or sunk panels with moulded margins, and by a cornice. The use of the dado raises the chief wall-decoration of the room to a level with the eye and prevents its being interrupted or concealed by the furniture which may be placed against the walls. This fact makes it clear that in all well-designed rooms there should be a dado about two and a half feet high. If lower than this, it does not serve its purpose of raising the wall-decoration to a line above the furniture; while the high dado often seen in modern American rooms throws all the rest of the panelling out of scale and loses its own significance as the pedestal supporting an order.
In rooms of the sixteenth and seventeenth centuries, when little furniture was used, the dado was often richly ornamented, being sometimes painted with delicate arabesques corresponding with those on the doors and inside shutters. As rooms grew smaller and the quantity of furniture increased so much that the dado was almost concealed, the treatment of the latter was wisely simplified, being reduced, as a rule, to sunk panels and a few strongly marked mouldings. The decorator cannot do better than plan the ornamentation of his dado according to the amount of furniture to be placed against the walls. In corridor or antechamber, or in a ball-room, the dado may receive a more elaborate treatment than is necessary in a library or drawing-room, where probably much less of it will be seen. It was not unusual, in the decoration of lobbies and corridors in old French and Italian houses, to omit the dado entirely if an order was used, thus bringing the wall-decoration down to the base-board; but this was done only in rooms or passage-ways not meant to contain any furniture.
The three noblest forms of wall-decoration are fresco-painting, panelling, and tapestry hangings. In the best period of decoration all three were regarded as subordinate to the architectural lines of the room. The Italian fresco-painters, from Giotto to Tiepolo, never lost sight of the interrelation between painting and architecture. It matters not if the connection between base and cornice be maintained by actual pilasters or mouldings, or by their painted or woven imitations. The line, and not the substance, is what the eye demands. It is a curious perversion of artistic laws that has led certain critics to denounce painted architecture or woven mouldings. As in imaginative literature the author may present to his reader as possible anything that he has the talent to make the reader accept, so in decorative art the artist is justified in presenting to the eye whatever his skill can devise to satisfy its requirements; nor is there any insincerity in this proceeding. Decorative art is not an exact science. The decorator is not a chemist or a physiologist; it is part of his mission, not to explain illusions, but to produce them. Subject only to laws established by the limitations of the eye, he is master of the domain of fancy, of that _pays bleu_ of the impossible that it is his privilege to throw open to the charmed imagination.