The great hall of assembly, which adjoined the vestibule, was generally the finest portion of the temple. The architraves supporting the roof rested upon a great number of lofty columns, which in the centre rose to a greater height, in order to obtain a clerestory, by which the hall was lighted. The largest of these is in the temple of Karnak, measuring 170 by 329 feet. The central avenue consists of twelve columns, 62 feet high by 11 feet 6 inches in diameter. Besides these there are one hundred and twenty-two others, 42 feet 6 inches in height and 28 feet in circumference. The lintel over the doorway by which it is entered measured 40 feet in length. The sanctuary was contiguous to the great hall, and terminated the suite. This consisted of a chamber, either occupying the whole of the rear space, or isolated by corridors on each side, with smaller sanctuaries opposite. In many of these, altars and statues have been found, some of the former formed of a single block, hollowed at the top and pierced through from top to bottom, so that sacrifices placed upon them could be consumed apparently without ignition, by means of fires kindled in subterranean vaults. In connection with the halls in the temple of Abydus and elsewhere there were a number of vaulted chambers; the vault not being formed of a series of true arches, that is, with joints radiating to a common centre, but consisting of stone beams placed one beside the other, and hollowed out on the under side. The arch, however, was not unknown to the Egyptians—there are stone vaulted tombs at Sakkarah of the time of Psammetichus (650 B.C.), and crude brick arches have been found at Thebes dating as far back as the period of the eighth dynasty (2925 B.C.?). The antiquity of the arch has been the subject of much debate, owing chiefly to the fact that the Greeks made no use of it; recent explorations have, however, shown that this constructive expedient was known both in Egypt and Assyria many years before it was adopted by the Etruscans, to whom its invention was long attributed. The exterior walls of all temples were built on a batter, sloping inward at an angle of about seventy degrees and with scarcely any openings. The inside walls were perpendicular, and decorated with bass-reliefs and paintings. These were often of a most elaborate character, and it is from them that so much has been learned concerning the ancient history of the country. The rock-cut temples of Nubia are laid out on much the same plan. They usually consist of a pronaos, naos, and sanctuary, forming a suite, with an entrance marked by colossal statuary hewn out of the side of the cliff. Some have a dromos of sphinxes, propylæa, and a peristyle court of masonry preceding the excavated portions. The temple of Wady Sabooah is the best example of the latter. Of the former none can compare with the Great and Small temples of Aboo Simbel, or Ipsambool, which are of the time of Rameses the Great.