In brief, the number of colours that could be used on the absorbent tin enamelled ground with its lead glaze was somewhat limited, consisting of blue, turquoise, yellow and orange. These colours are of great depth and translucency, and are only equalled by the blues and turquoise of China, Persia and India. Gubbio ware is frequently enriched with a raised curved fluting called “_Gadroons_,” a most effective method of enhancing the beautiful ruby lustre of Maestro Giorgio. This Gubbio tradition was continued by Giorgio’s son, Vincentio, called Maestro Cencio, and many beautiful lustre works are signed by him. This lustre was produced by exposing the ware to the action of smoke during the firing in the kiln; the smoke, being carbon in a highly divided state, reduces the metallic salts of the pigment or glaze, forming a thin film of metal upon the surface, the beautiful iridescent lustre resulting from the relative thickness of the film. Castel Durante was frequently enriched, on white or grey borders, with delicate raised scroll-work in white slip or enamel, a process called “_Lavoro di sopra bianco_” or “_bianco sopra bianco_.” Faenza Maiolica has, frequently, the whole surface of the ground covered with a dark blue enamel, enriched with dancing amorini and arabesques in blue, heightened with white “_Sopra Azzurro_.” A frequent form of enrichment upon plates was to have small medallions painted with portraits and appropriate inscriptions, and doubtless intended as lover’s presents. They are known as “_Amatorii Maiolica_.” TERRA COTTA. Terra Cotta is usually made from pure clay, which will burn to a white or yellow colour, or from impure, which will burn to a red colour, owing to the presence of oxide of iron. Pure clay is a hydrous silicate of alumina, containing 47 parts per cent. of silica, 40 of alumina, and 13 of water. Clay, in this proportion, is the Kaoline or china clay. Fire clay, which is found in the coal measures, has a larger proportion of silica than Kaoline, and from it much of the terra cotta is made. When first dug out, it is hard and compact, and of a greenish grey colour, deepening to black. It is often weathered before using. This causes it to “fall” and facilitates grinding. Old fire clay, previously burnt (“grog” as it is called) is added to the new clay to counteract the excessive shrinkage to which all close-grained clays are liable. The coarser the clay, the less the shrinkage. The colour of the clay varies according to the quantity of lime, iron, or bitumen it contains. Pure clay contracts as much as one-eighth from the size of the mould; one half of this contraction takes place in drying, the other half in burning. Clay mixed with “grog” will contract about one-twelfth. [Illustration]