Comfort and convenience united to take the cooking out of the atrium (which then became a reception-room) into a separate apartment known as the _culina_, or kitchen, in which was a raised platform on which coals might be burned and the processes of broiling, boiling, and roasting might be carried on in a primitive manner, much like the arrangement still to be seen at Rome. On the tops of the houses, after a while, terraces were planned for the purpose of basking in the sun, and sometimes they were furnished with shrubs, fruit-trees, and even fishponds. Often there were upwards of fifty rooms in a house on a single floor; but in the course of time land became so valuable that other stories were added, and many lived in flats. A flat was sometimes called an _insula_, which meant, properly, a house not joined to another, and afterwards was applied to hired lodgings. _Domus_, a house, meant a dwelling occupied by one family, whether it were an _insula_ or not. The floors of these rooms were sometimes, but not often, laid with boards, and generally were formed of stone, tiles, bricks, or some sort of cement. In the richer dwellings they were often inlaid with mosaics of elegant patterns. The walls were often faced with marble, but they were usually adorned with paintings; the ceilings were left uncovered, the beams supporting the floor or the roof above being visible, though it was frequently arched over. The means of lighting, either by day or night, were defective. The atrium was, as we have seen, lighted from above, and the same was true of other apartments--those at the side being illuminated from the larger ones in the middle of the house. There were windows, however, in the upper stories, though they were not protected by glass, but covered with shutters or lattice-work, and, at a later period, were glazed with sheets of mica. Smoking lamps, hanging from the ceiling or supported by candelabra, or candles, gave a gloomy light by night in the houses, and torches without. The sun was chiefly depended upon for heat, for there were no proper stoves, though braziers were used to burn coals upon, the smoke escaping through the aperture in the ceiling, and, in rare cases, hot- air furnaces were constructed below, the heat being conveyed to the upper rooms through pipes. There has been a dispute regarding chimneys, but it seems almost certain that the Romans had none in their dwellings, and, indeed, there was little need of them for purposes of artificial warmth in so moderate a climate as theirs.