These remarks apply as well to the decoration of pottery as to any other department of art work. Although from its peculiar nature and various uses this material yields itself to many and varied styles of decoration, yet this decoration, however simple, must be planned and executed according to sound principles, to be of any artistic value. The best preparation for the work of decorating pottery, therefore, is a thorough knowledge of drawing and an understanding of the laws which govern all decorative art. Sources of information upon these subjects, drawn from competent instruction, books and periodicals, are daily becoming more numerous and accessible, and one who desires to practice the kind of decorative art we are now considering, should cultivate his taste and augment his skill by these means, and especially by close study of nature in all its various forms. It is only in this way that the student will be enabled to accomplish work which will be a source of pleasure and profit to himself and others. POTTERY DECORATION UNDER THE GLAZE. CHAPTER I. POTTERY. We will consider in this chapter some facts in regard to pottery, which, although of a very elementary character, are not so generally understood as may be desirable. These facts relate to the substances of which pottery is composed, the processes of its manufacture, and the methods by which it is or can be decorated. Two chemical substances, viz., silica and alumina form the basis of all pottery clays. These substances are themselves infusible (except under the compound blow-pipe), but by admixture with other materials more susceptible to the action of heat, they are made useful to the potter’s art, and, when subjected to a high temperature, fuse and form the hard, insoluable combination with which we are all familiar. Porcelain, and the finer kinds of earthen-ware, are made from clays artificially combined of various natural elements, in such a manner as to produce the qualities desired, while the coarser wares are generally made from clays in a natural or unmixed state. These clays agree in their essential characteristics, but contain other elements which cause certain differences of color, susceptibility to heat, plasticity, etc. The differences, therefore, which exist between the many kinds of pottery manufactured, may be said to be due, not so much to a diversity of the materials used, as to the changes produced by the combination of the same materials in varying proportions. It is unnecessary that we should here enter into the details of the mixture of different pottery clays, for which each manufactory has its own formula. A few words, indicating, in a general way, the causes of certain easily-recognizable qualities, will suffice.