+ARCHITECTURAL DETAILS.+ There is no evidence that the Assyrians ever used columnar supports except in minor or accessory details. There are few halls in any of the ruins too wide to be spanned by good Syrian cedar beams or palm timbers, and these few cases seem to have had vaulted ceilings. So clumsy a feature as the central wall in the great hall of Esarhaddon’s palace at Nimroud would never have been resorted to for the support of the ceiling, had the Assyrians been familiar with the use of columns. That they understood the arch and vault is proved by their admirable terrace-drains and the fine arched gate in the walls of Khorsabad (Fig. 19), as well as by bas-reliefs representing dwellings with domes of various forms. Moreover, a few vaulted chambers of moderate size, and fallen fragments of crude brick vaulting of larger span, have been found in several of the Assyrian ruins. The construction was extremely simple. The heavy clay walls were faced with alabaster, burned brick, or enamelled tiles. The roofs were probably covered with stamped earth, and sometimes paved on top with tiles or slabs of alabaster to form terraces. Light was introduced most probably through windows immediately under the roof and divided by small columns forming mullions, as suggested by certain relief pictures. No other system seems consistent with the windowless walls of the ruins. It is possible that many rooms depended wholly on artificial light or on the scant rays coming through open doors. To this day, in the hot season the population of Mosul takes refuge from the torrid heats of summer in windowless basements lighted only by lamps.