Fig. 155.—Attic of the Great Hall at Karnak. Restored by Ch. Chipiez.
Fig. 156.—Claustra of the Hypostyle Hall, Karnak. Description, iii. 23.
The hypostyle hall at Karnak, with its lofty walls and close ranges of columns, would have been in almost complete darkness had it been left to depend for light upon its doors alone. But the difference of height between the central aisle and those to the right and left of it, was taken advantage of to introduce the light required for the proper display of its magnificent decorations. The wall which filled up the space between the lower and upper sections of roof, forming something almost identical with the clerestory of a Gothic cathedral, was constructed of upright sandstone slabs, about sixteen feet high, which were pierced with numerous perpendicular slits. Stone gratings, or claustra as the Romans would have called them, were thus formed, through which the sunlight could stream into the interior. The slits were about ten inches wide and six feet high. The illustration on page [163] shows how the slabs were arranged and explains, moreover, the general disposition of the roof. Fig. [156] gives the claustra in detail, in elevation, in plan, and in perspective.
The hypostyle halls are nearly always lighted upon the same principle. The chief differences are found in the sizes of the openings. At the Temple of Khons, where the space to be lighted was not nearly so large, the slabs of the claustra were much smaller and the openings narrower (Fig. [157]). In one of the inner halls at Karnak a different system has been used. The light penetrates through horizontal openings in the entablature, between the architrave and the cornice, divided one from another by cubes of stone (Fig. [158]). In the inside the architrave was bevelled on its upper edge, so as to allow the light to penetrate into the interior at a better angle than it would otherwise have done.
Fig. 157.—Claustra in the Hypostyle Hall of the Temple of Khons. Compiled from the elevations in the Description, iii. 28.
The use of these claustra, full of variety though they were in the hands of a skilful architect, were not the only methods of lighting their temples to which the Egyptians had recourse. They were helped in their work, or, in the case of very small chambers, replaced, by oblique or vertical openings contrived in the roof itself. These oblique holes are found in the superior angles of the hypostyle hall at Karnak (Fig. [159]). After the roof was in place it was seen, no doubt, that the claustra did not of themselves give enough light for the huge chamber, and these narrow openings were laboriously cut in its ceiling. One of the inner chambers of the Temple of Khons is feebly lighted by vertical holes cut through the slabs of the roof (Fig. [160]). Similar openings are to be seen in the lateral aisles of the hypostyle hall in the Ramesseum. The slight upward projection which surrounds the upper extremities of these holes should be noticed (Fig. [161]). Finally there are buildings in which these openings are the only sources of illumination. This is notably the case in the Temple of Amada. The upper part of our plan (Fig. [162]) represents the roof of that temple and the symmetrically arranged openings with which it is pierced.