A study of those reliefs in which nothing but purely ornamental motives are treated, leads us to exactly the same conclusion. Take for instance the great bronze threshold from Borsippa, of which we have already spoken; the rosettes placed at intervals along its tread are identical with those encountered in such numbers in Assyria. In the extreme rarity of stone in his part of the world the Chaldaean architect seems to have practically reserved it for isolated statues, for votive bas-reliefs, for objects of an iconic or religious character, but nevertheless, we have sufficient evidence to prove that such decorative sculpture as found a place in the Chaldaean buildings, did not sensibly differ from that to which Assyria has accustomed us. From all that we have said as to the distribution of stone, it will be understood that we must turn to Assyria to obtain a clear idea of the measures by which buildings of crude brick were rendered more sightly by ornament in the harder material. We can hardly imagine an Assyrian palace without those series of bas-reliefs which now line the walls of our museums much in the same fashion as they covered those of Sargon's and Sennacherib's palaces, and yet it is unlikely that in the beginning the Assyrian palaces had these carved walls. The casing of stone and alabaster must have been originally employed for more utilitarian purposes--to hide the grey and friable material within, to protect it from damage, and to offer a surface to the eye which should at least be inoffensive. The upper parts of the walls would be covered with a coat of stucco, which could be renewed whenever necessary, but for the lower part, for all that was within reach of the crowds that frequented the public halls of the seraglio, who passed through its gates or those of the city itself, some more efficient protection would be required. The constructor was thus led to encase the lower parts of his walls in a cuirass of stone imposed upon their brick cores. The slabs of which he made use for this purpose varied between three and ten feet in height, and between six and fifteen in width. Their average thickness was about eight inches.