So friable is old delft that it is prone to crip at the edges, there revealing the brown body base of the under clay. A drop of strong acid dropped on the body clay thus exposed will effervesce, since there is carbonate of lime in the understructure of old delft. This body clay is so soft that it is easily cut with a knife. This cannot be said of the English Lambeth delft, which English ware, though inspired by the old Dutch delft and contemporary with much of it, was of a much harder body base, denser and more glossy than the Dutch clay. The enamel lay much more closely and evenly to the body base in old Dutch delft than it did in the English delft. Dutch delft rarely crazed in the kiln; English delft often did so and in consequence its enameled surface came to be glazed to prevent this. Then one often finds the colors of the decoration of old Dutch delft to have run--neither under nor over the enamel surface but _into_ the enamel. This is because the colors were put upon the Dutch delft while the enamel was still wet and fixed in it during the liquefaction and fixing of the surface coating in the firing of the piece in the kiln. In such pieces of English delft as show the colors of their decoration to have run, it will be seen distinctly that these colors have run upon the enamel of the surface and not into or with it. Finally the color of the clay body of the Lambeth delft of England is buff. While nature has given us a sense of blue skies, scientists will tell you that she has been overly sparing with blue in flowers and in bird life. The Chinese had long placed this color as the first of the five nominated in their popular traditions. To blue they gave a symbolism rich and varied. They associated it with the East, for instance, and again with wood. It is natural that it should have been a favorite color for the Chinese ceramicist. The palace china of some of the early Chinese emperors reserved the privilege of blue decoration, a blue, as an old Chinese writer tells us, as “seen through a rift in the clouds after rain.” It was not until the sixteenth century that the Chinese obtained cobalt. This bright and vivid blue made speedy headway as against the grayer blues that until then had alone been produced by the Chinese ceramic artist. Cobalt was introduced into China by either the Jesuits or the Mohammedans; the Chinese themselves named the color “Moslem Blue.” The blue-and-white porcelain of China appears to have made a direct appeal to the Dutch potters. Blue was the earliest color used by them in their delft decoration. Purple followed, and after that the green, yellow, brown, and red of the polychrome delft pieces that we know.