This is proved by the dated contracts to which we have already so often had to refer; but supposing no such contracts to have been in existence we could have arrived at the same conclusion by another path. Cones in calcareous stone, in marble, or even in _pietra dura_ are either wanting altogether, or very few and far between; they are almost all in precious stones, most of them in carnelian and chalcedony. Sapphirine chalcedony, with its fine bluish tint, seems to have been most in favour. In Egypt we found intaglios upon metal as well as upon lapidary substances.[338] This use of metal was a result of mounting seals in circles of gold or silver. Precious stones were rare and difficult to cut; what could be more natural than to substitute metal for them and to make the bezel of a ring of the same material as its hoop. For its engraving neither lathe nor diamond dust was wanted; the burin alone was necessary, and the figures cut by it gave a result no less satisfactory than those obtained by the slower process and in the more stubborn material. The temptation was great for the Egyptian artist, and we are not surprised that he succumbed to it, but it did not exist for the Chaldæan engraver. The latter had only to deliver a stone which his client could wear fastened to his wrist, or hung round his neck by a cord. He had no direct and intimate relations with the worker in metal; he was not compelled to call in the latter to mount his creation. Sometimes, under the influence perhaps of foreign models, he may have attempted to substitute metal for stone, but isolated attempts did not make a school. We can point to only one example of such work. The British Museum possesses a silver cylinder, but the only interesting thing about it is its material.[339] The composition of the type is naive and its execution rough. All this allows us to believe that metal seals were very rare and never came into general use. Oriental artists, at least during the period of which we are now speaking, hardly ever practised any kind of gem-cutting but intaglio, but there are two stones in existence in which first attempts at a process that must have led in time to the production of cameos, may be traced. “In one of these gems, an onyx, the upper layer is cut away from the one below it and an inscription left. In the other the eyes and neck of a serpent are rendered with the aid of three different tints in the stone.”[340] § 9. _The General Characteristics of Chaldæo-Assyrian Sculpture._