The desire of rendering terracotta less porous, and of producing vases capable of retaining liquids, gave rise to the covering of it with a vitreous enamel or glaze. The invention of glass was attributed by the ancients to the Phoenicians; but opaque glass or enamels, as old as the Eighteenth Dynasty, and enamelled objects as early as the Fourth, have been found in Egypt. The employment of copper to produce a brilliant blue-coloured enamel was very early both in Babylonia and Assyria; but the use of tin for a white enamel, as discovered in the enamelled bricks and vases of Babylonia and Assyria, anticipated by many centuries the rediscovery of that process in Europe in the fifteenth century, and shows the early application of metallic oxides. This invention apparently remained for many centuries a secret among the Eastern nations only, enamelled terracotta and glass forming articles of commercial export from Egypt and Phoenicia to every part of the Mediterranean. Among the Egyptians and Assyrians enamelling was used more frequently than glazing; hence they used a kind of faience consisting of a loose frit or body, to which an enamel adheres after only a slight fusion. After the fall of the Roman Empire, the art of enamelling terracotta disappeared except amongst the Arab and Moorish races, who had retained a traditionary knowledge of the process. The application of a transparent vitreous coating, or glaze, to the entire surface, like the varnish of a picture, is also to be referred to a high antiquity. Originally intended to improve the utility of the vase, it was used by Greeks and Romans with a keen sense of the decorative effects that could be derived from its use. In Greece, although nearly all traces of the Stone Age are wanting, and little pottery has been found which can be referred to that period,[2] yet the earliest existing remains of civilisation are, as we shall see later, in the form of pottery; and Greece is no exception to the general rule. But the important difference between the pottery of Asia and Egypt and that of Greece is that only in the latter was there any development due to artistic feeling. Of the Greek it may be said, as of the medieval craftsman, _nihil tetigit quod non ornavit_. In the commonest vessel or implement in every-day use we see almost from the first the workings of this artistic instinct, tending to exalt any and every object above the mere level of utilitarianism, and to make it, in addition to its primary purpose of usefulness, “a thing of beauty and a joy for ever.” Feeble and rude it may be at first, and hampered by imperfect knowledge of technique or capacity for expression—but still the instinct is there.