The Diffusion of Light by Translucent Media in Antiquity: A Propos Two Alabaster Window-Pane Fragments from Ed-Dur (United Arab Emirates)
Potts, D. T., Antiquity
From a University of Copenhagen excavation in the United Arab Emirates come two fragments of sheet alabaster, from a large private house dated to the 1st century AD. They prompt consideration of alabaster's use for windows and of provision for natural lighting in the ancient buildings of the broad region, using ethnohistoric observations, medieval literary sources and ancient epigraphic evidence.
Whereas archaeologists (in particular classical archaeologists) have devoted a considerable amount of energy to the study of lamps, they have said very little about natural light and illumination in antiquity. The aim of this paper is to discussion means by which natural light was used and enhanced in ancient western Asia [ILLUSTRATION FOR FIGURE 1 OMITTED].
Illumination versus ventilation
About 1000 years ago the properties of a shaft of light entering a darkened room were discussed in detail by the renowned Arab physicist and mathemetician, Ibn al-Haytham (c. 965-1039) in one of his most important extant works, Fi 'l-daw' (Vernet 1971: 788-9; Baarmann 1882: 195-237). That this should have interested Ibn al-Haytham is not surprising, for in 10th- and early 11th-century Basra, where he was born, most houses probably suffered acutely from poor interior lighting. This is no slur on the quality of life in medieval Iraq,(1) rather it is a natural conclusion to draw given the type of house in which the bulk of the population probably lived, a standard type which had characterized southern Iraq since prehistoric times. O.E. Ravn (1942: 68) described the typical Iraqi or Babylonian house as follows:
There were no windows in the outer walls, and there was only one entrance. Within, one or more rooms opened on a court which was uncovered to give air and light. Possibly, as to-day, channels for ventilation were laid high up in the outer wall. During the hot season the direct rays of the sun are to be avoided, so the most characteristic arrangement of a house is to place the living-room - or the largest living-room - south of the court, and let only indirect light into the room and the doorway on the court.
Descriptions of traditional houses on Bahrain present us with a similar situation. In describing a Bahraini kitchen house as it looked in 1960, Henny Harald Hansen (1968: 40) wrote,
With the exception of the door there are no openings through which the light can enter. High up on the wails, some horizontal slits are found partly covered inside by square stone slabs in such a way that fresh air is allowed to enter. This arrangement therefore acts as a sort of air-conditioning.
These openings correspond to the roshien through which 'rising hot air was vented' in the traditional architecture of mainland eastern Saudi Arabia (Winterhalter 1981: 160) which were strictly differentiated from those intended to provide illumination. As Winterhalter (1981: 160) writes,
The rooms of houses in the old centres therefore had two rows of windows, one to provide light and the other to ventilate the rooms. The upper windows were small and always placed above the bigger windows, but directly below the ceiling.
Speaking again of Bahrain in 1960, Hansen noted that wooden frame windows with vertical, iron bars but without glass, bought ready-made in Manama, 'arrived late as a foreign element in traditional houses', but (Hansen 1968: 57),
There were none in the house which I inhabited. . . . It was one of the oldest houses in the village and the finest one architecturally speaking. The door was the only opening to the house. When it was closed at night fresh air entered through two small circular openings approx. 0.05 m. in diam., made through the hard coral limestone in one of the walls.
From all of this I would suggest that, in many studies of early architecture in western Asia, archaeologists have often confused apertures for ventilation with those intended to effect illumination, and thereby misunderstood their function completely. …