It is observed, from a technical point of view, that all the figures of one frieze came out of the same mould, and that they are exact repetitions one of another, though variously coloured. The vitreous coat is transparent and iridescent, like the enamel on porcelain; the gamut of the colours is poor: blue, green, yellow, black, and white. These decided tints must, on account of their brilliancy, have produced a striking effect; and under the hot sun of Susiana, the portico walls of Artaxerxes’ palace sparkled more marvellously than even the richly decorated tiles of Mussulman mosques and palaces. The interior of the apadâna seems to have been simply coloured by means of a red monochrome stucco, almost completely concealed, however, by the rich carpets and embroidered draperies with which the walls of all the chambers were hung. § IV. RELIGIOUS AND SEPULCHRAL MONUMENTS. Ormuzd (Ahura-Mazda), the great deity of the Persians, was not to have, according to the regulations in the Avesta, either temples or statues. The conception of the supreme and only God, perfect in all things, was too vast to suggest any shelter for him except the vault of heaven in which he dwelt. Herodotus did not fail to observe this characteristic of Mazdeism and this absence of temples among the Persians: “The custom of the Persians,” he says, “is not to raise statues, temples and altars to the gods; on the contrary, they treat those who do so as madmen: in my opinion, this is because they do not believe, like the Greeks, that the gods have a human form.” However, Ormuzd is often represented on the monuments of the Achæmenid dynasty; he has the form of a man crowned with the tiara and enclosed in a winged disk (fig. 141). This is exactly, except in the modifications brought about by the progress of art, the figure of the deity in the Assyrian monuments.[61] Thus this symbol, borrowed from Mesopotamia, is a transgression of the precepts of the Avesta, and an act of tolerance which only penetrated into the monumental sculpture of palaces and tombs, and into the glyptic art. The only symbol admitted by the Avesta is the all-purifying flame. Hence the cultus of the sacred fire and the fire-altars, called pyrea or _atesh-gahs_, erected in the open air on heights. The atesh-gahs are the only monuments which represent the religious architecture of the Persians. Their remains are numerous, but they do not present many features of archæological interest. Several of them are seen at a short distance from Nakhsh-i-Rustam which seem to be earlier than the time of Cyrus. On a platform reached on all sides by a few steps, an altar is erected in the form of a truncated pyramid, with four sides. At the corners small columns, attached to the structure, support semicircular arches, which sustain the stone slab on which the sacred fire was lighted. [Illustration: Fig. 138.--The tower of Jur. Restoration by M. Dieulafoy.]