Discovery of the metals and the means of working them are the two major developments in the history of human civilization. The names generally given to the three prehistoric periods of man's life on the earth - the Stone, the Bronze and the Iron age - imply the vast importance of the progressive steps from the flint knife to the bronze celt, and lastly to the keen-edged elastic iron weapon or tool.

Gold, silver, copper, tin, iron and lead were most popularly used metals in primitive ages. Their peculiarities have naturally marked out each of them for special uses and methods of treatment. The durability and the extraordinary ductility and pliancy of gold, its power of being subdivided, drawn out or flattened into wire or leaf of almost infinite fineness, have led to its being used for works where great minuteness and delicacy of execution were required; while its beauty and rarity have, for the most part, limited its use to objects of adornment and luxury, as distinct from those of utility. In a lesser degree most of the qualities of gold are shared by silver, and consequently the treatment of these two metals has always been very similar, though the greater abundance of the latter metal has allowed it to be used on a larger scale and for a greater variety of purposes.

The great fluidity of bronze when melted, the slightness of its contraction on solidifying, together with its density and hardness, make it especially suitable for casting, and allow of its taking the impress of the mould with extreme sharpness and delicacy. In the form of plate it can be tempered and annealed till its elasticity and toughness are much increased, and it can then be formed into almost any shape under the hammer and punch. By other methods of treatment, known to the ancient Egyptians, Greeks and others, but now forgotten, it could be hardened and formed into knife and razor edges of the utmost keenness. In many specimens of ancient bronze, small quantities of silver, lead and zinc have been found, but their presence is probably accidental. In modern times brass has been much used, chiefly for the sake of its cheapness as compared with bronze.

In beauty, durability and delicacy of surface it is very inferior to bronze, and, though of some commercial importance, has been of but little use in the production of works of art. To some extent copper was used in an almost pure state during medieval times, especially from the 12th to the 15th century, mainly for objects of ecclesiastical use, such as pyxes, monstrances, reliquaries and croziers, partly on account of its sof tness under the tool, and also because it was slightly easier to apply enamel and gilding to pure copper than to bronze (see fig. I). In the medieval period it was used to some extent in the shape of thin sheeting for roofs, as at St Mark's, Venice; while during the 16th and 17th centuries it was largely employed for ornamental domestic vessels of various sorts.

The noble metals, gold and silver, are found in the native state, and as is well known, gold and silver were used to make jewelry and sheet metal due to the great ductility and lustre of the pure metals. Some of the early rich finds of gold artifacts were from the cemeteries in Bulgaria in Europe (5th millennium BC) with accouterments of hammered and sheet gold. Some of the most elegant gold vessels made by the repousse technique come from the Mesopotamia (ca 2500 BC). Spectacular gold castings are known from ancient Pharaohnic Egypt, such as the enigmatic face of the young Pharaoh Tutenkhamen (ca 1300 BC). Early gold and silver ornaments from the Indian subcontinent are found from Indus Valley sites such as Mohenjodaro (ca 3000 BC). These are on display in the National Museum, New Delhi.

As in almost all the arts, the ancient Egyptians excelled in their metal-work, especially in the use of bronze and the precious metals. These were worked by casting and hammering, and ornamented by inlay, gilding and enamels with the greatest possible skill. From Egypt perhaps was derived the early skill of the Hebrews. Further instruction in the art of metal-working came probably to the Jews from the neighboring country of Tyre. The description of the great gold lions of Solomon's throne, and the leaver of cast bronze supported on figures of oxen, shows that the artificers of that time had overcome the difficulties of metal-working and founding on a large scale.

The Assyrians were perhaps the most remarkable of all ancient nations for the colossal size and splendour of their works in metal; whole circuit walls of great cities, such as Ecbatana, are said to have been covered with metal plates, gilt or silvered. Herodotus, Athenaeus and other Greek and Roman writers have recorded the enormous number of colossal statues and other works of art for which Babylon and Nineveh were so famed. The numerous objects of bronze and other metals brought to light by the excavations in the Tigris and Euphrates valleys, though mostly on a small scale, bear witness to the great skill and artistic power of the people who produced them; while the discovery of some bronze statuettes, shown by inscriptions on them to be not later than 2200 B.C., proves how early was the development of this branch of art among the people of Assyria.