Between China and the Spanish Moors exist a wide gap and centuries of time, in which glazed pottery and porcelain intended for the uses of domestic life seem to have been unknown. And this, too, was among the Greeks, the Phoenicians, the Romans--nations eager for every good thing, astute, keen, grasping. Among the remains of Roman art have been found a few pieces of pottery upon which are traces of the use of a glaze; but, if it was used at all, it seems to have been almost an accident--not at all as with us, to complete and perfect the work. To the Moors and the Moorish civilization of Spain, Europe owes the knowledge or the introduction of this most valuable art, which has enabled her to reach such perfection in the making of fictile ware as we now see and enjoy. Not only has the glaze (and enamel) given great strength to pottery, and increased its use to an infinite variety: it has also enabled most nations, beginning with the Chinese, to add to its beauty, and, indeed, to develop or create a method of artistic expression which is peculiar and most interesting. This subject will be treated more fully, in the progress of this work, in a chapter upon decorating porcelain and pottery. After the work of the Moors in Spain, which will be treated in a separate chapter, one of the earliest applications of the glaze in Europe was upon a hard sort of _stone-ware_ made at various places along the Rhine, and in Flanders and Germany. It has come to be known under a generic title of GRÈS DE FLANDRE, while but little of it was really made in Flanders. A great centre of its manufacture and sale, as early as the 1300's of our era, was at Cologne; and a more fit name for it would be Grès de Cologne; still, the usual name is the one the world knows it by. The body or paste of which this is composed differs from the faiences or earthen-wares of which we write. It is harder, heavier, and much more durable. The commoner kinds are made so by a considerable mixture of siliceous sand; while in the finer kinds, known as Grès de Flandre, there are mixed with the paste other clays, such as _terre de pipe_ and _kaolin_. This hard and heavy body has long been used for common stone-ware jugs and pots made for every-day use. In China it was and is still used as a body for vases and dishes, which received a covering or "engobe," and upon that an artistic finish--such as the crackle-vases, and many others. The glaze upon what we know as Grès de Flandre was made by using in the furnace common salt; the fumes of which, combining with the fused silex, resulted in what is termed the _salt-glaze_. This requires a high degree of heat, in which no colors will stay except the blue of cobalt, a brown, and a violet.