Paper trimmings are divided into four classes, white and mixed, soft and hard “shavings,” and are especially available, as they may be used after sorting and dusting without undergoing further treatment, but it is customary to macerate them in some sort of a pulper before placing with other stock in the beaters. The printed waste must be boiled in a solution of soda ash. This makes the ink removable. After about six hours’ boiling, the stock is transferred to washers and treated like rags. The ink and dirt having first been removed, bleaching solution is introduced, and finally the stock is let down into drainers. In some mills the draining is omitted, the excess bleach is washed out and an antichlor added; then the stock is pumped over to a beating engine to be mixed with the other ingredients preparatory to manufacture. This process is less thorough, and there is more danger of getting residues of bleach into the paper, as it is rather a nice matter to exactly neutralize the bleach in the washer, and the maintenance of a uniform color is endangered. Printers, or others, who accumulate large quantities of waste papers, will find that it pays to keep the various grades in separate receptacles, as a better price may be obtained for it in this way. Furthermore, by means of a baling press, the papers may be set aside in compact bales, which occupy less room and are not so great a fire risk as loose accumulations. The fact that 21.4 per cent of the paper-making fibers, according to United States Census Report, 1909, are derived from waste papers, indicates their importance as raw materials, while their use lessens the drain upon our forests. THE NON-FIBROUS CONSTITUENTS OF PAPER. The non-fibrous constituents of paper are the mineral fillers, the ingredients for sizing, and the coloring pigments and dyes. Mineral fillers should not be regarded as adulterants. They are used, not as a means for adding weight, but for the sake of certain effects which are requisite in many papers. No filler is used on good writings or ledgers, as the printing requirements do not call for a closely filled surface or a mellow texture. In book papers a varying percentage of clay is used, as it improves the printing quality by filling up the interstices between the fibers and increases opacity. Papers for half-tone printing require more filling, in order to have smooth, level surfaces. There are several kinds of filler in common use. The most common is China clay, of which the cleanest and finest grades are obtained principally in England. No equally good deposit has yet been successfully developed in this country. Clay is a product of the natural disintegration of feldspar. It is soft, plastic, and non-crystalline.