The floors were of stone, or a composition made of lime or other materials; but in humbler abodes they were formed of split date-tree beams, arranged close together or at intervals, with planks or transverse layers of palm branches over them, covered with mats and a coating of mud. Many roofs were vaulted, and built like the rest of the house of crude brick; and not only have arches been found of that material dating in the 16th century before our era, but vaulted granaries appear to be represented of much earlier date. Bricks, indeed, led to the invention of the arch; the want of timber in Egypt having pointed out the necessity of some substitute for it. Wood was imported in great quantities; deal and cedar were brought from Syria; and rare woods were part of the tribute imposed on foreign nations conquered by the Pharaohs. And so highly were these appreciated for ornamental purposes, that painted imitations were made for poorer persons who could not afford them; and the panels, windows, doors, boxes, and various kinds of woodwork, were frequently of cheap deal or sycamore, stained to resemble the rarest foreign woods. And the remnants of them found at Thebes show that these imitations were clever substitutes for the reality. Even coffins were sometimes made of foreign wood; and many are found of cedar of Lebanon. The value of foreign woods also suggested to the Egyptians the process of veneering; and this was one of the arts of their skillful cabinet makers. The ceilings were of stucco, richly painted with various devices, tasteful both in their form and the arrangement of the colors; among the oldest of which is the Guilloche, often miscalled the Tuscan or Greek border. Both in the interior and exterior of their houses the walls were sometimes portioned out into large panels of one uniform color, flush with the surface, or recessed, not very unlike those at Pompeii; and they were red, yellow, or stained to resemble stone or wood. It seems to have been the introduction of this mode of ornament into Roman houses that excited the indignation of Vitruvius; who says that in old times they used red paint sparingly, like physic, though now whole walls are covered over with it.