It would be very strange however, if in these palaces of the last of the Sargonids the decorator had deliberately renounced the beauties of that discreet system of polychromy of which the traces are to be found in all the earlier palaces. It is possible that these touches of colour were reserved for the last when the palaces were erected, and that something may have happened to prevent them from being placed on the sculptures of these two sovereigns. So far as we can discover, no trace of colour has been found on any of the arched steles or isolated statues left to us by Chaldæa and Assyria. This abstention is to be explained by the nature of the materials at the disposal of the sculptor in Chaldæa, the cradle of his art. These were chiefly igneous rocks, very hard, very close in grain and dark in colour, and susceptible of a very high polish. The existence of such a polish disposes of any idea that the figures to which it was given were ever painted. The pigment would not have stayed long on such a surface, and besides, the reds and blues known to the Ninevite artists would have had a very poor effect on a blue-black ground. On the other hand, when they set to work to model in clay the Assyrians could give free rein to their love for colour. Most of the statuettes found in the ruins of their palaces had been covered with a single uniform tint, which, thanks to the porous nature of the material, is still in fair preservation. The tint varies between one figure and another, and, as they are mostly figures of gods or demons, the idea has been suggested that their colours are emblematic.[288] Thus the Louvre possesses a statuette from Khorsabad representing a god crowned with a double-horned tiara, and covered all over, flesh and drapery alike, with an azure blue.[289] A demon with the head of a carnivorous animal, from the same place, is painted black, a colour that seems to suggest a malevolent being walking in the night and dwelling in subterranean regions.[290] The Assyrians also made use of what has been sometimes called natural polychromy, that is to say they introduced different materials into the composition of a single figure, each having a colour of its own and being used to suggest a similar tint in the object represented. Several fragments of this kind may be seen in the cases of the British Museum.[291] We may give as examples some eyes in black marble; the ball itself is ivory while the pupil and iris are of blue paste, a sandy frit in which the colour sank deeply before firing. Beards and hair were also made of this material; they have been found in several instances, without the heads to which they belonged. In the ruins from which he took these objects, Layard saw arms, legs and torsos of wood. They were so completely carbonized by fire that they could not be removed; at the least touch they crumbled into powder.