On some of the crosses the marks of the tool with which they were carved can still be clearly seen, as on the Cross of Iltyd at Llantwit Major, and the cross-base at Llangevelach, both in Glamorganshire. As far as it is possible to judge from the tool-marks, either a pick or a pointed chisel must have been employed by the early Christian Celtic stone-carvers. Similar tool-marks have been observed on the cup-and-ring sculptures of the Bronze Age. In the churchyard at Kells, Co. Meath, there is an unfinished cross which is of great interest as showing the exact methods used in the construction and decoration of this class of monument. The stone was first squared and the design roughly set out upon it. Draughts were then cut across the faces, leaving certain portions standing out in high relief, upon which the figure subjects were afterwards sculptured. The unfinished cross at Kells was formerly lying on the ground, but it has recently been erected on its original base, which is also unfinished. When the crosses are constructed of two or more pieces they are fitted together by means of mortice and tenon joints. Sometimes the quadrants of the circular ring connecting the arms were made in separate pieces, as in the case of the large broken cross at Iona.[434] The metals in use during the Christian Celtic period were gold, silver, copper, lead, bronze, brass, and other alloys. These were cast and wrought and ornamented by means of enamelling, niello, plating, gilding, repoussé work, chasing, engraving, piercing, inlaying, filigree-work, Trichinopoly chainwork, and settings of precious stones, amber, and glass. The different pieces of the metal objects were fixed together by rivets, and if soldering and brazing were known, they were certainly not employed to any great extent. Even when the specimens can be removed from their show-cases in museums and examined carefully by an expert it is not always possible to be certain of the exact technical processes by which the various decorative effects have been produced, and unless the objects can be dissected many of the constructive features must necessarily be a matter for conjecture. The Ardagh Chalice and the Tara Brooch illustrate nearly all the materials, technical processes, and methods of construction used at this period. [434] _Proc. Soc. Ant. Scot._, vol. xxxv., p. 90.