When we use the terms china clay or kaolin, we refer only to the white earthy pigments of silica and alumina, that are used in paints and colors. We pass by the species of earth known as pipe clay, potters' clay or fire clay, for which there is no use in paint making, because of their color and other special characteristics. While the general term for white clay is kaolin, this name is used among our trade for the white clay mined in various parts of the United States, principally in Alabama and South Carolina, but also in some Northern localities. This will answer many purposes in the line of paint manufacture, but where a really soft and very white material of this character is required the imported article known as china clay, which is mined and prepared for export at Cornwall, England, is preferred. Pigments equaling this English china clay are also found in other countries, notably in Germany and France, but for commercial reasons hardly ever imported into this market. G. H. Hurst, in his work on "Painters' Colors, Oils and Varnishes," describes the origin, and also the manufacture of china clay, as it is being carried on at the clay works at Cornwall, so that it will be unnecessary to devote space to the subject here. All the white clays for use in paint must consist of silica and alumina with some combined water, otherwise they will not fulfill their function. The texture varies somewhat according to this composition, some being more unctuous than others. If silica were not present in the pigment it would have no tooth whatever and with oil produce a liverlike mixture. The china clay that by chemical analysis approaches closest to the following composition may be considered best for general use in paint; 47 per cent silica, Si02; 39 per cent alumina, AL203; 13 per cent water, H20 (allowing 1 per cent for free moisture, magnesia, potash and iron). The color maker will, however, prefer the pigment that is entirely free of iron oxide. Domestic kaolin will vary somewhat from this analysis, generally consisting of more silica and showing appreciable fractions of one per cent of iron oxide and lime. Still fairly large quantities are being used of the domestic article in many special paints, where light weight per gallon is desirable. When china clay is imported it comes in large casks, two to the long ton, and the clay is in lump form, usually containing anywhere from 6 to 10 per cent moisture that has to be driven off before it can be bolted for the use of the paint maker, hence the price of bolted China clay is so much in advance over the quotation of the importer. Enormous quantities of this clay are imported for industrial purposes, where it is used in the pulped form and in that case the amount of moisture cuts a figure only as to its weight. The clay absorbs some moisture in transit and on being stored in the open on wharves, hence the large percentage of water usually found.