No trace has yet been found of any mould used by the Sumerians in the process of casting metal, but we may assume that clay was employed both for solid and hollow castings. While many figures of the same form have been found, no two are exactly alike nor of quite the same proportions, so that it may be inferred that a mould was never used a second time, but that each was broken in order to remove the casting. The copper foundation-figures usually take the form of nails, terminating with the bust of a female figure, and they were set in a socket beneath stone foundation-inscriptions which they support. Later, votive objects, cast in copper, represent male figures, bearing on their heads the builder's basket, in which is clay for the sacred bricks of the temple's foundation; or they consist of great cones or nails supporting a recumbent bull,[37] or clasped by the kneeling figure of a god.[38] Large figures of wood were sometimes covered with thin plates of copper joined by a series of small nails or rivets, as is proved by the horn of a bull of natural size, which has been discovered at Tello.[39] But hollow castings in copper of a considerable size have also been found. A good example is the bull's head, figured in the accompanying block, which probably dates from a period not later than the close of Ur-Ninâ's dynasty. Its eyes are inlaid with mother-of-pearl and lapis-lazuli, and a very similar method of inlaying is met with in the copper head of a goat which was found at Fâra.[40] [Illustration: Fig. 25--One of a series of copper female foundation-figures with supporting rings, buried in a structure of unburnt brick beneath stone foundation-records. From Tello; period of Ur-Ninâ. _Déc._, pl. 2 _ter_, Fig. 3.] A far simpler process of manufacture was employed for the making of votive figures of terra-cotta, which, in order of development, preceded the use of metal for this purpose, though they continued to be manufactured in considerable quantities during the later periods. Here the mould, in a single piece, was cut in stone or some other hard material,[41] and the clay, after being impressed into it, was smoothed down on the back by hand. The flat border of clay left by the upper surface of the mould, was frequently not removed, so that the figures are sometimes found standing out from a flat background in the manner of a sculptured plaque, or bas-relief. In the period of Gudea, the mould was definitely used as a stamp, thus returning to the original use from which its later employment was developed. Interesting examples of such later stamped figures include representations of a god wearing a horned headdress, to which are added the ears of a bull, and of a hero, often identified with Gilgamesh, who holds a vase from which two streams of water flow.[42] The clay employed for the votive figures is extremely fine in quality, and most of them are baked to a degree of hardness resembling stone or metal.